24 Now Thomas, one of the twelve, named Didymus, was not with them when Jesus came. 25 So the other disciples said to him, We have seen the Lord. But he said to them, If I do not see in his hands the print of the nails and put my finger into the print of the nails, and if I do not put my hand into his side, I will never have belief.
26 And after eight days, his disciples were again in the house and Thomas was with them. Though the doors were shut, Jesus came, and taking his place in the middle of them, he said, May peace be with you! 27 Then he said to Thomas, Put out your finger, and see my hands; and put your hand here into my side: and be no longer in doubt but have belief. 28 And Thomas said in answer, My Lord and my God!
Matthew Henry's Commentary on John 20:24-28
Commentary on John 20:19-25
(Read John 20:19-25)
This was the first day of the week, and this day is afterwards often mentioned by the sacred writers; for it was evidently set apart as the Christian sabbath, in remembrance of Christ's resurrection. The disciples had shut the doors for fear of the Jews; and when they had no such expectation, Jesus himself came and stood in the midst of them, having miraculously, though silently, opened the doors. It is a comfort to Christ's disciples, when their assemblies can only be held in private, that no doors can shut out Christ's presence. When He manifests his love to believers by the comforts of his Spirit, he assures them that because he lives, they shall live also. A sight of Christ will gladden the heart of a disciple at any time; and the more we see of Jesus, the more we shall rejoice. He said, Receive ye the Holy Ghost, thus showing that their spiritual life, as well as all their ability for their work, would be derived from him, and depended upon him. Every word of Christ which is received in the heart by faith, comes accompanied by this Divine breathing; and without this there is neither light nor life. Nothing is seen, known, discerned, or felt of God, but through this. After this, Christ directed the apostles to declare the only method by which sin would be forgiven. This power did not exist at all in the apostles as a power to give judgment, but only as a power to declare the character of those whom God would accept or reject in the day of judgment. They have clearly laid down the marks whereby a child of God may be discerned and be distinguished from a false professor; and according to what they have declared shall every case be decided in the day of judgment. When we assemble in Christ's name, especially on his holy day, he will meet with us, and speak peace to us. The disciples of Christ should endeavour to build up one another in their most holy faith, both by repeating what they have heard to those that were absent, and by making known what they have experienced. Thomas limited the Holy One of Israel, when he would be convinced by his own method or not at all. He might justly have been left in his unbelief, after rejecting such abundant proofs. The fears and sorrows of the disciples are often lengthened, to punish their negligence.
Commentary on John 20:26-29
(Read John 20:26-29)
That one day in seven should be religiously observed, was an appointment from the beginning. And that, in the kingdom of the Messiah, the first day of the week should be that solemn day, was pointed out, in that Christ on that day once and again met his disciples in a religious assembly. The religious observance of that day has come down to us through every age of the church. There is not an unbelieving word in our tongues, nor thought in our minds, but it is known to the Lord Jesus; and he was pleased to accommodate himself even to Thomas, rather than leave him in his unbelief. We ought thus to bear with the weak, 1 John 5:11.