Both the Gospels and Paul (quoting an earlier tradition) specify that there were 12 special followers (1 Corinthians 15:5; Matthew 10:1-4; Mark 3:13-19; Luke 6:12-16; John 6:67-71). The synoptics, however, name a total of 13, 11 of them in common (Luke disagrees with Matthew and Mark about the name of the 12th, thus providing a 13th name). John’s Gospel names another disciple, Nathanael (John 1:45-51), who is not mentioned in the synoptics. The early Christians seem to have had 12 as a firm number, but they were not certain who should be included. It is probable that Jesus himself spoke of “the twelve,” though he was not necessarily followed all the time by precisely 12, nor by precisely the same people. If this is right, the value of the number was symbolic: “the twelve” represented the 12 tribes of Israel. Jesus promised the disciples that “in the new world, then the Son of man shall sit on his glorious throne, you who have followed me will also sit on 12 thrones, judging the 12 tribes of Israel” (Matthew 19:28). This has the effect of “enthroning” Judas, who was one of the 12 on everyone’s reckoning, despite the fact that Judas betrayed Jesus. The early Church, knowing of Judas’ betrayal, would not have invented a promise from Jesus that would give Judas a place in the new age, and thus we may accept the saying as authentic.
The use of 12 as a symbolic number and the explicit reference to the 12 tribes points to a very concrete expectation: that the 12 tribes of Israel would be restored. Centuries earlier the Assyrians had scattered ten of the tribes. Obviously it would take an act of God to get them all back together. Numerous Jewish authors hoped that this would happen. Ben Sira (c. 200 B.C.E.) looked to God to “gather all the tribes of Jacob” and “to give them their inheritance, as at the beginning” (Ben Sira 36:11, cf. 48:10). The sect associated with the Dead Sea Scrolls (probably a branch of the Essene party) expected the reassembly of the 12 tribes (The War Scroll [1QM]). The same expectation appears in the pseudepigraphical Psalms of Solomon 11, 17:28-32, 50 and elsewhere. The tradition was continued in early Christianity (Revelation 21:12).
Jesus himself was a Bible-believing Jew, and like many others he thought that God would honor his promises to the patriarchs and restore the 12 tribes in the last days—just as God had previously wrought miracles on behalf of the dead.
Apparently the disciples thought that they would play in important role in the kingdom that God would establish. In the passage quoted above (Matthew 19:28), Jesus promised to enthrone them in the role of judges. In another passage the disciples debate among themselves about who is greatest. Jesus rebukes them by saying that those who wish to be first should be last (Mark 9:33-35). More significantly, James and John (who, with Peter, were leading disciples) asked if they could sit on Jesus’ right and left in his “glory” (Mark 10:35-45). It seems that there was some dispute among the disciples about who would have the leading places in the kingdom. (E.P. Sanders, “The Life of Jesus” in Hershel Shanks, ed. Christianity and Rabbinic Judaism: A Parallel History of Their Origins and Early Development [London: SPCK, 1993], 41-83, 336-37, here, pp. 52-3)
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