Who will judge the 12th tribe of Israel?

I can't say anyone but God knows that , but we all shall. However, I'm inclined to say I suspect it is Dismas,the good thief.

The apostles represented every walk of Jewish life, and it was their complete repentance, deserting all to follow Jesus, that makes their very existance a judgement on all who did not repent.

As such, Dismas was a thief who repented.

But maybe, then again, we're mistranslating "judge". Weren't the judges of the Old Testament biblical heroes through whom God wrought great deliverance? In that sense, the twelvth judge would have to be Paul.

I don't see why it could not be Judas. Granted, Jesus made this statement to the remaining 11 disciples after Judas had left the room. However, Judas expressed obvious remorse and regret over his betrayal of Jesus as he killed himself. Similarly, if 1 Peter 3:18-20 means Jesus in body or spirit did preach the gospel to those in Hades after His death, since Judas died before Jesus, if he had not repented before his death he would have had the chance to repent at that time. I agree, though, that we cannot know and won't until we see it in person.

For the record, I don't agree with Matthias but could see it being Paul. Or maybe just the 11 of "y'all" :)

I think it will be Matthias who was chosen by the apostles to fill in the place of Judas right after the Lord's ascension in the very beginning of Acts. Number twelve was a vey important number for Jews, hence, it was the very first thing they did after the Lord commanded them to go to Jerusalem and await the infilling with the Holy Spirit.

Assuming Affable Geek is right about the Greek, then that would largely explain it. One thing about English, unlike ancient Greek (and many other languages, like Spanish which I know a lot of), is that in English, we use the same word for the second-person singular and second-person plural. In other words, we say "you" whether addressing one person or many. In Greek, it's clear what is being said (if it is you or y'all).

Regarding the apostleship, it is interesting that originally there were 12, and then one was replaced, but by 2, sort of; do you know what that sounds like? The 12 tribes of Israel! There were 12 sons of Israel, yet one of them, Joseph, gave his lot to his 2 sons. In reality, the "twelve" tribes are, for all intents and purposes, 13 (though they are considered twelve because each of Joseph's sons got half a share). Yet the Old and New Testaments consistently refer to the 12 tribes of Israel (except when discussing them in technical matters, because God can count, lol). This is complicated all the more by the fact that Revelation 7:8 refers to the tribe of Joseph, then refers to the tribe of Manasseh (one of Joseph's sons) who had a half-share in Jacob's blessing, and then leaves out Dan (one of Jacob's 12 sons) and Ephraim (Joseph's other son) completely! There are all kinds of theories as to why this is, but whatever the case, even the tribes themselves are treated with a great deal of fluidity, just like with the apostles.

With that said, as to where Paul and Matthias come into play with the judging of the 12 tribes, I'm not sure it is 100% clear; my guess would be that the 13 collectively judge the 12 tribes, which in itself is an idea not clearly described in the Bible, so that's just speculation on my part.

Why are you assuming a one to one correspondence? The Greek here says "y'all" will judge them. The idea is that collectively you will bear witness against all of Israel.

In Greek, the verse is:

ἵνα ἔσθητε καὶ πίνητε ἐπὶ τῆς τραπέζης μου ἐν τῇ βασιλείᾳ μου, * καὶ καθήσεσθε ἐπὶ θρόνων τὰς δώδεκα φυλὰς κρίνοντες τοῦ Ἰσραήλ.

κρίνοντες is a verb (to judge - from which we get 'criminal') which is in the 2nd person plural, meaning that "You" is "y'all" (aka plural) and not singular.

If you need a one to one correspondence, take your pick between Matthais or (my personal bet as the real 12th apostle) Paul. But there's no reason too.

One person can judge multiple people, and multiple people can judge one.