John 20:19-29
19 When it was evening on that day, the first day of the week, and the doors were locked where the disciples were, for fear of the Jews, Jesus came and stood among them and said, “Peace be with you.” 20 After he said this, he showed them his hands and his side. Then the disciples rejoiced when they saw the Lord. 21 Jesus said to them again, “Peace be with you. As the Father has sent me, so I send you.” 22 When he had said this, he breathed on them and said to them, “Receive the Holy Spirit. 23 If you forgive the sins of any, they are forgiven them; if you retain the sins of any, they are retained.”
24 But Thomas (who was called the Twin), one of the twelve, was not with them when Jesus came. 25 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.”
26 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.” 27 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.” 28 Thomas answered him, “My Lord and my God!” 29 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.”

BACKGROUNDER
Jesus offers his friends a much-needed peace when he rises from the dead. And then he sends them out from their hiding place. He breathes his Spirit into them, to empower them for his mission of mercy.
Why is the breathing of the Holy Spirit so important? Recall that when God first created people he breathed life into them (Genesis 2:7). Jesus breathes into them so that they will have a share in God’s divine life (2 Peter 1:4), making them new creations (2 Corinthians 5:17). This is the promise of mercy: despite our separation of God because of sin, thanks to the cross of Jesus, we now have hope of eternal life.
In order to undertake the mission of mercy the disciples have to overcome fear. They have locked themselves for fear that they too would be arrested and crucified as Jesus had been. This is a rational fear, but it leaves them trapped.
Jesus’ gift of the Spirit changes all that. Soon they will go into action, when they are “filled with the Holy Spirit, and they spoke the word of God with boldness” (Acts 4:31).
The mercy that they are to preach has a source: Jesus. He is risen, meaning that in the power of God Jesus has overcome the power of sin and death. But when he is risen, he shows the wounds which he endured on the Cross. The mercy of the Cross will begin to flow out from Jesus, through the disciples, to the whole world.
Thomas shows faith in Jesus when he cries out, “My Lord and my God!” This is the saving faith that opens the doors of mercy. The Mercy of the Cross, received by those who put their trust in Jesus, is only received when we share it. The mission of mercy is for sinners, like you and me.