After Jesus had appeared to his other disciples in their house, one of them named Thomas was not there.
The other disciples told him that they saw Jesus, but he said that he would not believe that Jesus had been resurrected until he saw the nail marks in Jesus' hands, and the cut in his side from the soldier's spear.
A week later Jesus came and again appeared inside the disciples house, even though all the doors were locked.
He said "Peace be with you!"
Then he said to Thomas "Put your finger here; see my hands. Reach out your hand and put it into my side. Stop doubting and believe.".
Thomas said "My Lord and my God!"
Jesus said to Thomas "Because you have seen me, you have believed; blessed are those who have not seen and yet have believed."
Because Thomas doubted whether Jesus was really alive, he is sometimes called Doubting Thomas.
(from: wikipedia - doubting thomas)
Kid Facts - Blast from the past: Blessed are the merciful
