20:19. Now when it was late the same day, the first of the week, and the doors were shut, where the disciples were gathered together, for fear of the Jews, Jesus came and stood in the midst and said to them: Peace be to you.
The doors were shut… The same power which could bring Christ's whole body, entire in all its dimensions, through the doors, can without the least question make the same body really present in the sacrament; though both the one and the other be above our comprehension.
20:20. And when he had said this, he shewed them his hands and his side. The disciples therefore were glad, when they saw the Lord.
20:21. He said therefore to them again: Peace be to you. As the Father hath sent me, I also send you.
20:22. When he had said this, he breathed on them; and he said to them: Receive ye the Holy Ghost.
20:23. Whose sins you shall forgive, they are forgiven them: and whose sins you shall retain, they are retained.
Whose sins, etc… See here the commission, stamped by the broad seal of heaven, by virtue of which the pastors of Christ's church absolve repenting sinners upon their confession.
20:24. Now Thomas, one of the twelve, who is called Didymus, was not with them when Jesus came.
20:25. The other disciples therefore said to him: We have seen the Lord. But he said to them: Except I shall see in his hands the print of the nails and put my finger into the place of the nails and put my hand into his side, I will not believe.
20:26. And after eight days, again his disciples were within, and Thomas with them. Jesus cometh, the doors being shut, and stood in the midst and said: Peace be to you.