Augustine of Hippo

(de Con. Ev. l. iii. c. 25.) This manifestation of our Lord after His resurrection, John also relates. But when John says that the Apostle Thomas was not with the rest, while according to Luke, the two disciples on their return to Jerusalem found the eleven gathered together, we must understand undoubtedly that Thomas departed from them, before our Lord appeared to them as they spoke these things. For Luke gives occasion in his narrative, that it may be understood that Thomas first went out from them when the rest were saying these things, and that our Lord entered afterwards. Unless some one should say that the eleven were not those who were then called Apostles, but that these were eleven disciples out of the large number of disciples. But since Luke has added, And those that were with them, he has surely made it sufficiently evident that those called the eleven were the same as those who were called Apostles, with whom the rest were.

But let us see what mystery it was for the sake of which, according to Matthew and Mark, our Lord when He rose again gave the following command, I will go before you into Galilee, there shall ye see me. Which although it was accomplished, yet it was not till after many other things had happened, whereas it was so commanded, that it might be expected that it would have taken place alone, or at least before other things.