John 20:25

The other disciples therefore said unto him, We have seen the Lord. But he said, Except I shall see in his hands the print of the nails, and put my hand into his side, I will not believe.

Eight days (Sunday to Sunday) elapsed between the two appearances with Thomas absent and Thomas present; and during that period he found his way back to the group. He had once affirmed that he would die with the Lord (John 11:16); but, like the others, he had failed. However, he came back, and that is what counts. He came back, and Jesus came back to meet him. Jesus came back to the man who came back; and therein is a promise of hope for all who will return to the Master. There can be no doubt that the second of these Lord's Day appearances was primarily for the benefit of the absentee.

Naturally, the others told Thomas what had happened; but he said, in effect, that he would not believe unless he received the same evidence they had witnessed; and the marvel of marvels is that Jesus simply came back and gave it to him, incidentally giving double corroboration to the entire apostolic group.