St. John (20:19–29) records two appearances of the Risen Christ in the Upper Room. On Easter Sunday evening, with the doors shut for fear of the Jews, Jesus came and stood in the midst: 'Peace be to you.' He showed them His hands and side, breathed on them, and gave them the Holy Spirit and the power to forgive sins.
Thomas, called Didymus, was not with them. The other disciples said: 'We have seen the Lord.' He answered: '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.'
Eight days later, the disciples were again within, and Thomas with them. Jesus came, the doors being shut, and stood in the midst: 'Peace be to you.' Then He said to Thomas: 'Put in thy finger hither, and see my hands; and bring hither thy hand, and put it into my side; and be not faithless, but believing.' Thomas answered: 'My Lord and my God' — the great confession of the divinity of Christ in the New Testament. Jesus replied: 'Because thou hast seen me, Thomas, thou hast believed: blessed are they that have not seen, and have believed.' This last word is addressed to every Christian of every age after the Apostles.