On the night on of the Resurrection Jesus appeared to the disciples in the same room where the Last Supper had occurred. The doors were locked and the disciples were frightened about what was to come next. Jesus showed them his wounds. He commissioned them to carry the Gospel then breathed on them, said "Receive the Holy Ghost", and gave them the power to forgive sins. (John 20:19-23.)
In the image above we see Tissot's presentation of the event in a watercolor entitled The Appearance of Christ at the Cenacle, at the Brooklyn Museum.
But Thomas was not present for this event and did not believe what others told him. Jesus appeared again eight days later and that time Thomas was present. Jesus invited Thomas to touch his wounds and Thomas believed. Jesus said that Thomas had seen and believed, but blessed are those who believe without seeing. (John 20:24-29)
Below is Tissot's The Disbelief of St. Thomas showing this event.



