What does it mean to be "poor in spirit"?

The word ptōchos used means absolute poverty.

Spiritually speaking, the poor in spirit are those who recognize their utter lack of the Spirit. This is the first step one must recognize during conversion - that he lacks and need the Holy Spirit. Thus the poor in spirit are the ones who are blessed, because, unlike the proud Pharisees, they recognize with the help of God their utter poverty, and receive the help they need.

Couple this with the second verse "blessed are those who mourn." The word penthéō is a type of deep grieving like there is a death in the family. Christians are not called to be unhappy people, but only those who recognize their need of the Holy Spirit can then see their sins so clearly that they mourn sin.

Finally Revelation 3:17-18 further expands the need of recognizing that we are poor:

17 Because you say, ‘I am rich, have become wealthy, and have need of nothing’—and do not know that you are wretched, miserable, poor, blind, and naked— 18 I counsel you to buy from Me gold refined in the fire, that you may be rich; and white garments, that you may be clothed, that the shame of your nakedness may not be revealed; and anoint your eyes with eye salve, that you may see.

Poverty of spirit is nothing more than humility.

"First He lays down humility as a foundation," writes Theophylact.¹

Since Adam fell through pride, Christ raises us up by humility; for Adam had aspired to become God. The "poor in spirit" are those whose pride is crushed and are contrite in soul.²

"The pauper in spirit," wrote the 19th century Russian preacher John of Kronstadt, "is the person who sincerely admits he is a spiritual pauper, with nothing to call his own."³

He waits for everything form God's mercy alone, he is convinced that he can neither think nor wish anything good if God does not give him a good thought or a good impulse, he knows that he cannot perform even one truly good deed without the grace of Jesus Christ. He considers himself worse, more sinful, and lower than everyone else; he always blames himself and does not judge anyone; he acknowledges his soul's raiment to be foul, dismal, stinking, and good-for-nothing; and he does not cease to implore the Lord Jesus Christ to enlighten the raiment of his soul, to clothe him in the imperishable garment of righteousness. He runs unceasingly to the shelter of God's wings, not having any safety in the world save for the lord. He considers all his inheritance to be God's gift and earnestly thanks the Giver for all good things for it, and gladly gives a part of his inheritance to those who ask it. This is who is poor in spirit.⁴

^{1 The Explanation of the Holy Gospel According to St. Matthew, p.44
2 Ibid.
3 Ten Homilies on the Beatitudes (Cornerstone Editions, 2003), p.26
4 Ibid., pp.26-27}

What does it mean to be “poor in spirit”?

Mat 5:3 Blessed are the poor in spirit: for theirs is the kingdom of heaven.

poor = ptōchos =

Thayer Definition: 1) reduced to beggary, begging, asking alms 2) destitute of wealth, influence, position, honour 2a) lowly, afflicted, destitute of the Christian virtues and eternal riches 2b) helpless, powerless to accomplish an end 2c) poor, needy

A distinction is made in "poor" such that the widow with two mites is called poor (pentichros) as needy but with some meager resources. The poor of "ptōchos" have nothing and no hope of anything. I once talked with a Greek scholar about the word "ptōchos" and he said that the sound of the word was the sound made when you would spit on someone and he thought that was the origin of the word.

Barkley describes a progression in the meaning of the word from one having no resources or hope of resources to having deep faith as a result of having nothing else in which to hope. If this is correct, one might see the addition of "in spirit" in Matthew not as an error or addition, but as an expansion that reflects this use of the word "poor".

The Old Testament and Hebrew linguistic background of this passage should be kept in mind. Recall:

• Matthew (or his source) was likely translating words that were spoken in Hebrew or Aramaic.
• Both Jesus and Matthew likely had a Semitic mother tongue.
• The Hebrew bible (both in its Hebrew and Greek forms) was frequently referenced explicitly by both, and in many more cases provided unstated background.

The term used is οἱ πτωχοὶ τῷ πνεύματι, (hoi ptōchoi tō pneumati) – "the poor in [or with respect to] spirit". The dative translated "in" has a broad range of meanings; this needs to be determined from context. A few relevant points of context from the Hebrew scriptures:

1. The Psalms, regarding poor.

   The word ptōchos is the preferred (thought not exclusive) translation of the Hebrew עני (ʿānî) which carries the basic idea of "lacking" – at times in the sociologic sense (lacking property), but more often in the Psalms it denotes "neediness" with reference to God. See especially Psalms 10 and 72, where it is also sometimes translated "afflicted". As far as I see, in all of its 31 appearances in the Psalms ʿānî is used in a positive sense, characterizing those who recognize their need of God. ¹

2. Psalm 51:17,* regarding spirit.

   The sacrifices of God are a broken spirit;
      a broken and contrite heart, O God, you will not despise.

   The "spirit" here is pneuma in the Greek Septuagint, the same word used in Matthew 5. This provides a background for the idea that having a pneuma that is "compromised" in some way is a rhetorical indication of humility toward God.

3. Isaiah 66:2, regarding poor in spirit.

   All these things my hand has made,
      and so all these things came to be,
      declares the LORD.
   But this is the one to whom I will look:
      he who is humble and contrite in spirit
      and trembles at my word.

   The word that the ESV translates "humble" is ʿānî (see #1, above), and "spirit" is translating ruach, the normal Hebrew correlate of pneuma. Here "humble and contrite in spirit" is helpfully restated: "trembles at my word."

_{*All quotes are ESV.}

<sup>Note
1. In this way, Luke’s "poor" that parallels Matthew’s "poor in spirit" (Luke 6:20 // Mat. 5:3) may carry the same sense (or even translate the same Semitic term?), despite the fact that the Greek ptōchos itself more often refers to economic disadvantage.</sup>

^{References
R. T. France, The Gospel of Matthew (NICNT; Eerdmans, 2007).}

^{Ludwig Koehler, Walter Baumgartner, et al., The Hebrew and Aramaic Lexicon of the Old Testament (Leiden; New York: E.J. Brill, 1999).}

^{William Arndt, Frederick W. Danker and Walter Bauer, A Greek-English Lexicon of the New Testament and Other Early Christian Literature, 3rd ed. (Chicago: University of Chicago Press, 2000).}

^{The links in the body of the answer are to older lexicons, provided for convenience because they are freely available. It is the newer lexicons cited here that were used to inform this answer.}