Where did Theophrastus write about a "a common chest" into which funds are placed in case of a member's hardship?

Theophrast did not write about this directly in an overly explicit and extensive way, but he indeeds gives several hints on these, in his Characters.

This answer complements @kimchilover's answer.

The institution sought after is ἔρανος (eranos). Which is now often translated as 'loan', 'loan-application' or 'subscription'. That this was first translated/described by scholars like Casaubon as communem arcam/ 'common chest' makes this somewhat difficult to find and follow. But the established institution of eranos is named several times in Theophrast's work, without much fundamentals a the 'grand scheme' of how this worked, but with more some illuminating details in how different people behaved within that framework, and a few hints on what this meant in practice not found elsewhere.

The concept or institution of eranos is properly explained as:

The name is derived from the Ancient Greek word ἔρανος meaning "a banquet to which the guests bring contributions of food, a no-host dinner."

— en:WP

Or in more detail:

Eranos (Greek ἔρανος) in ancient Greece referred to an association that made contributions for a specific purpose, e.g. for the ransom from captivity or slavery, payment of a fine or for a common feast. Eranos was also the name of the collected property and the purpose of the collection (e.g. payment).
Homer used ἔρανος in the Odyssey to denote a simple, ordinary meal with regular participants who contributed to it (Od. 1, 226). The έρανος in modern Greek means a specific fund-raising or fund-raising action.
In classical Athenian democracy, the Eranos association constituted a separate legal entity from the 6th century BC onwards. The association had the function of a credit union and was set up in accordance with its statutes to provide for the needy. Economic historians therefore see it as a prototype of the insurance system. The Eranos Association included provisions of personal, procedural and property law. In addition, it had active and passive procedural law, i.e. it could sue and be sued.

— de:WP, translated

Since both Wikipedia articles as well as most web searches are dominated by the modern theology association named in this manner, in

The Oxford Classical Dictionary reports:

Eranos was essentially concerned with *reciprocity: at first of food, and later of money. In *Homer, eranos refers to a meal for which each diner contributed a share (Od. 1. 226); alternatively, the venue might be rotated. This earlier meaning was never lost (Xen. Mem. 3. 14. 1); but, by the later 5th cent. bce, the concept had evolved to include a *credit system, common in Athens, whereby contributors lent small sums to help out a common acquaintance in need (Lys. 20. 12; cf. Pl. Ap. 38b). The strong obligation to lend was matched by a reciprocal obligation to repay as soon as possible. The reciprocity inherent in the eranos-idea is reflected in metaphorical usage: to die in battle for the polis was to offer one's kallistos eranos (‘finest contribution’), receiving in return ‘immortal praise’ (Thuc. 2. 43. 1). Readiness to contribute towards eranos loans could be cited in Athenian courts as an aspect of civic virtue (Antiphon 2. 2. 12); failure to repay as indicative of general degradation (Lys. fr. 1 Carey). Disputed is the extent to which eranists in Athens were ad hoc groupings, or fixed associations (see clubs, greek), somewhat resembling friendly societies.

In the New Pauly we read:

Eranos (ἔρανος; éranos).

[1] Collective fund
[2] Private association

Etymology uncertain; the word originally meant ‘a meal for friends’ (Hom. Od., Pind.). The cost was borne in common by the participants. Collections made among friends in order to present a gift to one of them were also called éranoi; to give gifts in return was merely customary, not a statutory obligation (Theophr. Char. 17,9). Two legal institutions developed on this basis:

[1] Collective fund

A kind of collective wealth. Funds (eisphoraí) collected by a group of individuals (plērōtaí, Dem. Or. 21,184f.) were applied to a particular purpose (payment of a fine, payment of a ransom, purchase out of slavery) in favour of a beneficiary. The fund was named after the initiator of its collection: this was often the beneficiary himself. The funds were transferred to the beneficiary purely as an interest-free loan for the purpose stipulated; the members of the fund could take an action for return of the amount (but see Pl. Leg. 11,915e).

[2] Private association

A particular type of private association was also called eranos; see Associations.

Loan

— Thür, Gerhard (Graz), “Eranos”, in: Brill’s New Pauly, Antiquity volumes edited by: Hubert Cancik and , Helmuth Schneider, English Edition by: Christine F. Salazar, Classical Tradition volumes edited by: Manfred Landfester, English Edition by: Francis G. Gentry. Consulted online on 06 June 2022 doi.

This is curious as it lists Characters XVII, but as in kimchilover's answer we read:

6 καὶ φίλῳ δὲ ἔρανον κελεύσαντι εἰσενεγκεῖν εἰπών, ὅτι οὐκ ἂν δοίη, ὕστερον ἥκειν φέρων καὶ λέγειν, ὅτι ἀπόλλυσι καὶ

— Characters. Theophrastus. Hermann Diels. Oxford. Oxford University Press. 1909.

— Thphr. Char. 15.7

Which is about the 'Grouchiness' person, translated in Loeb's Classical Library 225 as:

After first refusing to give to a friend who has asked him to contribute to a loan, he comes to him later and brings it, but adds that he is throwing his money away again.

— J. M. Edmonds: "The Characters of Theophrastus Newly Edited and Translated", William Heinemann: London, 1929.

This character is also translated as "self-centered man" and:

If a friend asks for a contribution to a loan he at first refuses, then comes along with it and says that this is more money wasted.

— James Diggle: "Theophrastus Characters", Cambridge University Press: Cambridge, New York, 2004.

Or in Jebb's translation:

XV. The Surly Man (iii)

Surliness is discourtesy in words. […] Then, if a friend asks him for a subscription, he will say that he cannot give one; but will come with it by and by, and remark that he is losing this money also.

Now, the lexicon say on ἔρα^νος , ὁ,:

A.meal to which each contributed his share, picnic, “εἰλαπίνη ἠὲ γάμος ; ἐπεὶ οὐκ ἔρανος τάδε γ᾽ ἐστίν” Od.1.226, cf. 11.415 : metaph., Pl.Smp.177c. 2. generally, feast, festival, Pi.O.1.38 ; “πολύθυτος ἔ.” Id.P.5.77 ; wedding-banquet, ib.12.14, Pherecyd.11 J.; “ἔρανον εἰς θεοὺς..ἐποίεις” E.Hel.388.

II. loan raised by contributions for the benefit of an individual, bearing no interest, but recoverable at law, in instalments, “παρὰ τῶν φίλων ἔ. συλλέξαι” Antipho 2.2.9, cf. Thphr.Char.22.9 ; κομισόμενος τὸν ἔ. recover the loan, Arist.Ph.196b34 ; “ἔ. εἰσενεγκεῖν τινι” Thphr.Char.15.7, Philem.213.14 ; “ἔ. τινι εἰς τὰ λύτρα εἰσφέρειν” D.53.8 ; “ἔ. εἰς ἐλευθερίαν” Id.59.31, cf. GDI2317 (Delph.), al.; “ἔ. ἀναλαμβάνειν” BGU 1165.16 (i B. C., with mention of interest); “ἔ. εἰκοσίμνως” Lys.Fr.19 ; “πεντακοσιόδραχμος” SIG1215.5 (Myconos); “διτάλαντον εἶχες ἔ. [δωρεὰν] παρά τινων” D.18.312 : in pl., debts thus contracted, Ar.Ach.615 (prob.), Hyp.Ath.9 ; τοὺς ἐ. διενεγκεῖν pay off such debts, Lycurg.22 ; ἐράνους λέλοιπε he has left repayment-instalments unpaid, D.27.25 ; ἔ. συνεφήβοις ἀπενεγκεῖν (cf. infr. III) Luc. DMeretr.7.1.

2. metaph, τοὐράνου γάρ μοι μέτεστι: καὶ γὰρ ἄνδρας εἰσφέρω (spoken by Lysistrata), Ar.Lys.651 ; “δεῖ τοῖς γονεῦσι τὸν ὡρισμένον ἐξ ἀμφοτέρων ἔ. καὶ παρὰ τῆς φύσεως καὶ παρὰ τοῦ νόμου δικαίως φέρειν” D.10.40, cf. 21.101, Isoc.10.20, Pl.Lg.927c ; “κάλλιστον ἔ. [τῇ πόλει] προϊέμενοι” Th.2.43, cf. X.Cyr.7.1.12, Ph.2.553, etc.: generally, favour, service, esp. one which brings a return, “κάλλιστον ἔ., δοὺς γὰρ ἀντιλάζυται” E.Supp.363 ; “ἔ. ἀντιλαμβάνειν” Arist.Pol.1332b40 ; “ἀποδοῦναι” Alex.280 ; ironically, τὸν αὐτὸν ἔ. ἀποδοῦναι 'pay him back in his own coin', D.59.8. III. a permanent association apparently religious in character (cf. ἐρανιστής), IG12(1).155.12 (Rhodes, ii B.C.), 22.1369 (Athens, ii A. D.); ἔ. συνάγειν Μηνὶ Τυράννῳ ib.3.74 ; “καλεῖται ὁ αὐτὸς καὶ ἔ. καὶ θίασος” Ath.8.362e ; functioning as a friendly society, Plin.Ep.Trai.92 ; it could apparently lend to a non-member, “ὅρος χωρίων ὑποκειμένων τῷ ἐ. καὶ τῷ ἀρχεράνῳ” SIG1198 (Amorgos, iii B. C.), cf. BGU1133-6 (i B. C.).

Another hint we glean from Theophrast in 22,9 "Parsimony"

10 ἔνδον μένειν, ὅταν ἐκδῷ θοἰμάτιον ἐκπλῦναι: καὶ φίλου ἔρανον συλλέγοντος καὶ διειλεγμένου αὐτῷ, προσιόντα προϊδόμενος ἀποκάμψας ἐκ τῆς ὁδοῦ τὴν κύκλῳ οἴκαδε πορευθῆναι:
Characters. Theophrastus. Hermann Diels. Oxford. Oxford University Press. 1909. — Thphr. Char. 22.9

is translated as:

If a friend is raising a subscription, and has spoken to him about it, he will turn out of the street when he descries him approaching, and will go home by a roundabout way.

— R. C. Jebb

Or in 'grumbling man'

XVII. The Grumbler (xxii)

… If a subscription has been raised for him by his friends, and someone says to him ‘Cheer up!’ — ‘Cheer up?’ he will answer; ‘when I have to refund his money to every man, and to be grateful besides, as if I had been done a service!’

— Jebb

Similarly, in "I. The Ironical Man (v)", Jebb we see:

To applicants for a loan or a subscription he will say that he has no money; when he has anything for sale, he will deny that he means to sell; or, when he does not mean to sell, he will pretend that he does.

As well as:

XXII. The Mean Man (xxv)

Meanness is an excessive indifference to honour where expense is concerned.

When subscriptions for the treasury are being made, he will rise in silence from his place in the Ecclesia, and go out from the midst.

And:

This he declares is what he contributed to these poor men's subscription-lists, adding that he takes no account whatever of the trierarchies and other state-services he has performed.

— XXIII. Pretentiousness (Loeb)

What can historians make of these?

One type of arbitration, by public officials, has been seen as especially prominent after the 330s when dated lists of public arbitrators start to survive in Attic inscriptions. Eranoi are knonw epigraphically on several Attic horoi from later fourth century and have been inferred at deme level, most recently in the newly-published text of the deme of Kollytos in the 320s. […]

The Characters' eranoi and arbitrations, by contrast, were not promised or allotted in a public assembly. Theophrastus is not alluding to Attica's boards of elderly public arbitrators but to the casual activity of private 'third parties' who might be appealed to at any time during others' disputes. Like the random 'arbitrators' who are sometimes cited in surviving Attic orators, the Affable Man becomes involved, but tries to please both parties: the Tactless Man starts the participants quarrelling again: the Arrogant Man gives his decision while still in the street. So, too, the eranoi conform to those which we meet in the Attic orators, contributions raised by 'collectors' from groups of willing participants and made available to a person in need. They were interest-free, but usually made as loans to be repaid, though not always with such a formal security as we might infer from the examples inscribed on surviving horoi. Repayment was expected, but perhaps not always enforced. 'Be cheerful', the Grumbling Man is told when his friends have arranged such a 'whip-round' for an éranos to him. 'How so,' he replies, 'when I must give the money back to each of them, and besides that, I owe a favour as one who has been done a good turn?' Modern studies of reciprocity could well use this text as their epigraph: Demosthenes, too, assumes that an éranos is not just something to be repaid, but is also a claim on the recipient to do a similar favour another time.

By studying democracy's public institutions, we are prone to underestimate these informal networks among Athenian friends and citizens: the private arbitrations of others' differences and the 'helping whip-rounds' in times of difficulty were important tests of a citizen's temper, already cited by Antiphon in the fifth century and exactly described by Theophrastus, alert to Attic practice and convention. No doubt there the polis' since the time of Hesiod. Since Solon's reforms, rather, Athen had been freed from formal ties of dependence and since 508, nearly two centuries of democracy had helped to entrench a sense of community among Athenian equal rights of citizenship. At Athens, above all, anyone might find hi to arbitrate or to bow to the pressure of an éranos for a friend or fellow-citizen. The Characters' ready references to them encourage us to emphasize otherwise encounter incidentally in Athenian evidence.

In his fine book, Paul Millett has recently studied and emphasized the Characters' allusions to lending and borrowing: in all, the collection has 'almost thirty to credit operations'. They remind us of the distinction between usurers and bankers, that not every lender at interest was a banker and that all sorts of objects be borrowed between friends. This emphasis on 'non-professional' loans is a useful economic reminder, but there are tantalizing hints about attitudes too.

— R. J. Lane Fox: "Theophrastus' "Characters" And The Historian", Proceedings of the Cambridge Philological Society, No. 42, pp.127–170, 1996. (jstor)

The book referenced here is:

Wherever there is a debtor there must also be a creditor, but Comedy naturally stresses the negative side of the relationship. For a more balanced picture of lending as well as borrowing, there are the Characters of Theophrastus, dating from the final decades of the fourth century. This short text, consisting of thirty brief character sketches or caricatures of people who might be met on the streets of Athens, has almost thirty references to credit operations. The Characters themselves, all of whom are unpleasant or foolish types, repeatedly display their negative qualities by adopting anti-social attitudes towards lending and borrowing.

— Paul C Millet: "Lending and Borrowing in Ancient Athens", Cambridge University Press: Cambridge, New York, 1991, p5. With numerous more elaborations on what can be gleaned from Theophrast, when correlated with other information.

This question turns out to be complex, with complex answers, so a road-map is in order.

I would re-title your question "Did Theophrastus write about a 'Common Chest…' and if so, where?".

The 19th century reformers of the English welfare system often mention ancient Greek practices involving a "common chest". They often cite a standard description of these practices that appears in book written by Isaac Casaubon in 1593 about Theophrastus's Characters, which is an essay on personality types that tangentially refers to Greek social insurance methods. Casaubon, to make Theophrastus's text clearer, describes these methods in some detail.

An unsigned editorial in a 1850 law reporting journal reviews a 1850 work by William Tidd Pratt as asserting that Theophrastus himself described these chests. The OP was unable to locate copies of this 1850 work online, and online copies of later editions of this work lack any reference to Theophrastus. The first edition of Pratt's 1850 book is pretty rare, and only a few libraries have copies (the British Library only has a microfilm copy of the Bodleian Library's copy, for instance), which possibly explains the lack of a scan.

It seems most likely to me that this edition of Pratt mentions Casaubon's commentary on Theophrastus's Characters and the anonymous reviewer miseard what Pratt wrote. Or possibly Pratt asserts Theophrastus himself described the common chest, possibly citing some other authority. It seems less likely to me that Pratt does not mention Theophrastus at all, because the anonymous reviewer seems in general to be pretty careful about quotations and so on. Other possibilities (such as Pratt citing a newly discovered MS by Theophrastus on Athenian poor laws) seem effectively impossible to me.

That's the road-map.

The short answer to the reformulated question is no, but Isaac Casaubon (1559-1614) did. Your sources are the victims of false attribution.

All the quotations in your question present versions of the following, as it appears in a 1717 English edition of Pufendorf's De iure naturae et gentium:

The Greeks took an excellent Method to ſupport their Friends in Diſtreſs : For ſeveral entred into a Society, and had a Common Cheſt, to which each contributed a certain Sum every Month; and out of this they lent Money without Intereſt to any one of the Society, that should happen to be reduc'd' to Neceſſity ; upon Condition to refund it, if his Circumſtances ſhould ever happen to grow better (d) (e).

This passage does not appear in the first (Lund, 1672) edition of Pufendorf's book but does in the Lausanne & Geneva edition of 1744. I do not know if it was added by Pufendorf's editor Jean Barbeyrac (1674-1744); but footnote (e), which refers to Casaubon's commentaries on Theophrastus's Characters, was added by Barbeyrac.

This account of the Athenian common chest is repeated in Melmoth's Dublin, 1748 edition of the letters of Pliny the Younger and re-repeated in an unsigned 1833 article in the Quaker journal The Yorkshireman. I am grateful to LangLangC for supplying another instance, in an essay (dated 1801, printed 1802) by Thomas Barnard, "Introductory Letter to the Third Volume" of Reports of the Society for Bettering the Condition and Increasing the Comforts of the Poor, pp.1-43. In a page-long footnote starting on p.33, Barnard summarizes Casaubon's statement in his commentaries in greater detail than I give below.

So the Athenian common chest was widely known in the 18th and 19th centuries, and when described usually is credited to Casaubon's Commentary.

Pufendorf's footnote (e) refers to Casaubon's 1593 edition of Theophrastus, in particular to his commentary on the "16th" chapter of Theophrastus's Characters.

((Casaubon's book starts its page numbering over three times (for the Greek text portion, for the Latin translation portion, and for Casaubon's commentary).
Adding to the confusion is the fact that Casaubons lists Theophrastus's chapters differently from the modern way used by the Project Gutenberg edition of Theophrastus's Characters.))

Casaubon gives a table of contents on scan frame #16, the 16th item of which is the chapter on the "surly man" (Αὐθάδεια, de ferocitate) which is chapter 15 in the usual numbering. The passage needing explanation is line 7:

καὶ φίλῳ δὲ ἔρανον κελεύσαντι εἰσενεγκεῖν εἰπών, ὅτι οὐκ ἂν δοίη, ὕστερον ἥκειν φέρων καὶ λέγειν, ὅτι ἀπόλλυσι καὶ, τοῦτο τὸ ἀργύριον.

meaning

Then, if a friend asks him for a subscription, he will say that he cannot give one; but will come with it by and by, and remark that he is losing this money also. [Jebb]

or, in the Project Gutenberg translation:

If you ask for his contribution to some object, he refuses to make one, though afterwards he may bring it around, declaring, however, that he’s throwing the money away. [Bennet & Hammond]

Casaubon's commentary spans pp.194–205 (scan pages #300–#311) of the 1593 Lyon edition, studded with references and quotations which I have not digested; his argument seems to have been accepted by classicists ever since. Casaubon explains the word ἔρανον appearing in the line in question.

On page 201 (#307) of Casaubon's commentary appears

Sic enim lego, non compulerunt: Porrò autem videntur ea fini & apud Athenienſes & in aliis Græcorum ciuitatibus inftitutæ ſodalitates quæ communem arcam; haberent, in quam quot menſibus certum quid à lingulpthreadsis pēderetur, vt efſent vnde iuuari poſsét qui ex illa ſodalitate fortunam aduerſam aliquo modo eſſent experti…

which after correcting for ligatures and the long s, Google "translates" as

For thus I read, they did not oblige; but furthermore, it seems that those associations were established both among the Athenians and in the other Greek states, which had the common ark [=chest], into which number of months certain things were to be paid by each one, so that they might be able to assist those who had in some way experienced the fortune which had been incurred by that company from that company.

It is clear that this discussion of the Greek sodalities with their common chests is part of an explanation of "contribution" or "subscription" in Theophrastus's description of the surly man of whom "If you ask for his contribution to some object, he refuses to make one…"

So some careless reader of a version of Melmoth or of Pufendorf with Barbeyrac's footnotes (or of some similar work citing Casaubon) was led to believe that the description of the common chest and so on was claimed to be Theophrastus's, instead of Casaubon's. If this reader was not the anonymous author of the 5 October 1850 opinion piece in Justice of the Peace, it is someone he relies on. Inspection of the rare-seeming 1850 edition of W. Tidd Pratt's book that he cites, (copies of which seem to exist in the State Library of Iowa, the National Library of Scotland, the University of Cambridge, the British Library, the Bodleian library, and Heidelberg) should clarify this issue.

The co-occurence of the words Theophrastus, Common, and Chest make it seem very likely that the ultimate source of Hardwick's statement was a work such as Melmoth's or Puffendorf's.

What follows is an attempt to trace exactly what the route of transmission was. That is, how did the topos of the common chest migrate from the world of classical scholarship to the world of advocacy for friendly societies?

A search for phrases in your quotation hits on a 1826 article "Remarks on Friendly Societies" by "N.O.", appearing in the The Monthly Magazine, new series volume 1, pp.484–489. On page 484 this appears:

The castes among the Hindoos; have some affinity to them in that particular point. Among the Athenians and other Grecian States, associations were instituted having a common chest, into which a certain monthly contribution, paid by each individual, was deposited; that a fund might be raised for relieving such members of that society, as might in any manner have experienced adverse fortune.*

with a footnote reading

Vide Becher's Observations, &c.—we have inserted the instance of the Athenians since the Essay was composed, not being before aware of the existence of Mr. Becher's last work.

I suppose "Becher" is John Thomas Becher, (1770–1848), see also. In 1826 he wrote "Observations upon the Report from the Select Committee of the House of Commons on the Laws respecting Friendly Societies, exemplifying and vindicating the principles of Life Assurance adopted in calculating the Southwell Tables, together with the heads of a Bill for improving the constitution and management of such institutions." It seems reasonable to assume this work is what N.O.'s footnote refers to. On p.483, N.O. comes to

…the main point of our article. Mr. John FLEMING, the present member for Hampshire, having deeply studied the subject, and availed himself of every source of information, with the forethought of a statesman…

John Fleming has a mixed reputation: negative, positive, and neutral. Apparently in 1826 he was in favor of Friendly Societies and hence in N.O.'s favor. (There is an interesting-looking paper about these people, behind a paywall.)

This leads to several questions.

Who was N.O.? What does his footnote mean? That the story about the Athenians and other Grecian States is borrowed from Becher's Observations or that it is not borrowed from Becher? What is the relation between N.O.'s statement about the Athenians and Hardwick's statement?