The Gospel for this Sunday has Jesus coming to his disciples who are locked up for fear of the Jews. Jesus comes and says, "Peace be with you." He then shows them his hands and his side. Then he said to them "Receive the Holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained."
Here we have the mercy of Jesus giving us the Sacrament of Reconciliation. And, of course, Jesus is showing His Divine Mercy to each of them. Thomas was not with them so then Jesus returns a week later when Thomas is with the others. Thomas had told the others that "Unless I see the mark of the nails in his hands and put my finger into the mark of the nails in his hands and put my finger into his side, I will not believe."
Jesus came again and stood in their midst and said, "Peace be to you." Then He said to Thomas, "Put your finger into my hands, and bring your hand and put it into my side, and do not be unbelieving, but believe. Thomas said, "My Lord and my God!" Something that many of us were taught to say at the moment of the consecration in the Mass.
Then Jesus said to him, "Have you come to believe because you have seen me? Blessed are those who have not seen and have believed."