In this selection from John, there are three main parts the last of which (vv. 30-31) is the conclusion to the Gospel. The first two parts (vv. 19-23;24-29) bring together two themes: the commissioning of the witnesses of the Risen Lord and what the Lord thinks about the faith of the those who have not seen yet believe.
The Commissioning of the Witnesses (vv. 19-23)
I have written something about this section here: Reading Guide for the Gospel of John. Jesus was sent by the Father to complete the work he was commanded to do. Now he sends his apostles in turn for a particular objective: the forgiveness of sins. For this mission, the Holy Spirit is given to them. The mission, however, is not something discontinuous with that of Jesus. "As the Father has sent me, " the Risen One says, "so I send you." This "As ... so ..." statement puts the mission of the apostles in a particular perspective: their job extends the one of Jesus. With the death and resurrection of Jesus, forgiveness for the sins of humanity both past and present has been won. The work of the apostles is to announce this good news and invite each generation of humanity to accept this gift and make it their own.
The Faith Of Those Who Have Not Seen (vv. 24-29)
The section is a pronouncement story, the punchline of which is in v. 29: "Because you have seen me, you have believed? Blessed are those who have not seen yet believe." The phrase "see ... believe" is found only three times in the Resurrection narratives of John.
In John 20:8, the disciple whom Jesus loved saw the linen wrappings in the tomb and believed. He has not yet seen the Risen One, only the signs of His rising, but he believed. He is like someone seeing the first glimmer of dawn and with certainty concludes: "Morning is here!" (For more of this, see the post "He Saw and He Believed"
In John 20:25, Thomas who was absent the first time the Risen Lord appeared declares:
Unless I see
the holes that the nails made
in his hands
and can put my finger
into the holes they made
and unless I can put my hand
into his side,
I refuse to believe.
The concern of Thomas is to verify that the same one who died on the cross is the one that has appeared before the other disciples. When the Lord first appears to the disciples, he showed them his hands and side (v.20). In Luke 24:36f, he not only shows his wounds, he also eats with the disciples to show them that he was still in the flesh, and not a ghost. When Thomas sees and touches the wounds (the Lord commands him to touch them), he confesses: "My Lord and My God." This is the climax of the confessions about Jesus made by the disciples: first he is "Messiah" (1:41), then "Son of God" (1:49), and with Thomas, "Lord God" (20:28).
In reply to this, Jesus says: "Because you see you now believe? Blessed are those who have not seen but believe." The reference here is about those who will believe in Jesus upon the word of the disciples (cf. John 17:20-24). By this macharism, the Lord is saying that those who will believe in Him upon the word of the apostles has a faith that is in no way inferior to that of those who have seen Him risen from the dead.
