When it was evening on that day, the first day of the week, and the doors of the house where the disciples had met were locked for fear of the Jews, Jesus came and stood among them and said, ‘Peace be with you.’ After he said this, he showed them his hands and his side. Then the disciples rejoiced when they saw the Lord. Jesus said to them again, ‘Peace be with you. As the Father has sent me, so I send you.’ When he had said this, he breathed on them and said to them, ‘Receive the Holy Spirit. If you forgive the sins of any, they are forgiven them; if you retain the sins of any, they are retained.’Thomas earned the moniker "Doubting Thomas" because his statement,
But Thomas (who was called the Twin), one of the twelve, was not with them when Jesus came. So the other disciples told him, ‘We have seen the Lord.’ But he said to them, ‘Unless I see the mark of the nails in his hands, and put my finger in the mark of the nails and my hand in his side, I will not believe.’
A week later his disciples were again in the house, and Thomas was with them. Although the doors were shut, Jesus came and stood among them and said, ‘Peace be with you.’ Then he said to Thomas, ‘Put your finger here and see my hands. Reach out your hand and put it in my side. Do not doubt but believe.’ Thomas answered him, ‘My Lord and my God!’ Jesus said to him, ‘Have you believed because you have seen me? Blessed are those who have not seen and yet have come to believe.’
Now Jesus did many other signs in the presence of his disciples, which are not written in this book. But these are written so that you may come to believe that Jesus is the Messiah, the Son of God, and that through believing you may have life in his name.
‘Unless I see the mark of the nails in his hands, and put my finger in the mark of the nails and my hand in his side, I will not believe.’Just remember that the other disciples were shown those same stigmata when Jesus appeared to them earlier. How many of them would have doubted if they had not been shown Jesus hands and side?
Those who were not first hand witnesses to the resurrected Jesus may have been envious of those who had seen Him, but Jesus' blessing of "those who have not seen and yet have come to believe" must have served as an encouragement to the early hearers of John's Gospel then just as it is an encouragement for us now, for we, like generations of Christians before, have not seen.
Today, we need all the encouragement we can get, for we live in an age in which the credibility and reliability of eye witness accounts are increasingly doubted.
In the case of Thomas, we have an example of something like the scientific method (in which an experiment must be duplicated by an independent researcher) at work. Jesus appeared once in the locked room, and when this was repeated, we got an affirmation of the original account. So, thanks to Thomas showing up late, we end up with the testimony of multiple witnesses to one event being confirmed by the second event using a new, skeptical investigator.