John Lightfoot on John 20:24

[But Thomas, called Didymus, was not with them.] I. The evangelist does not here, as the writers of lexicons, render the signification of a Hebrew name into Greek, when he tells us, "Thomas is also called Didymus"; but only lets us know that as he was called Thomas among the Hebrews, so was he called Didymus among the Greeks. There is not another amongst the twelve apostles of whom this is said. Simon indeed is called Peter; but these are really two distinct names: so was Nathanael called Bartholomew: but Thomas and Didymus both one name, of one signification in different languages. Perhaps Thomas was born in some place where the Jews and the Greeks promiscuously inhabited: such a place was the region of Decapolis; and so by the Hebrews he might be called by his Hebrew name, and the Greek by the Greeks.

II. The disciples had all fled and were dispersed when Christ was apprehended, Mark 14:50, except Peter and John. Whence it is said in verse 2 of this chapter, that Mary Magdalene came to Peter, and "to the other disciple, whom Jesus loved"; for she knew where she might find them; and so she could not for the rest. And thus scattered, as it should seem, they passed over the sabbath day; but when they heard that their Lord was risen, then they begin to associate again. But as yet Thomas had not got amongst them; and indeed Peter himself had been absent too, but that having seen the Lord he returned from Emmaus.

III. Thomas therefore not being present when our Saviour breathed on the rest and gave them the Holy Ghost, are we to suppose that he, by his absence, was deprived of this gift and privilege? No surely, for it was a privilege common to the whole apostolate, and peculiar to them as Apostles: so that however by his absence he might have missed of it, yet by reason of his apostolacy he could not. St. Paul, distant with a witness while these things happened, both from the apostleship and religion too, yet when made an apostle, was withal adorned with this privilege.