Luke composed his gospel and the Acts of the Apostles not only to tell his readers about the things Jesus said and did during his earthly and risen ministry, but also to teach his readers how to participate in that ministry.
We especially hear this latter aspect of his writing in today's Acts pericope. Luke begins by mentioning, "Many signs and wonders were done among the people at the hands of the apostles." Then, after describing how the sick tried to have Peter's shadow "fall on one or another of them," he ends by stating, "A large number of people from the towns in the vicinity of Jerusalem also gathered, bringing the sick and those disturbed by unclean spirits, and they were all cured."
It appears Luke, and all our early Christian authors, interpreted Jesus' Last Supper words, "Do this in memory of me!" as applying to more than just his words and actions during that particular meal. They believed everything they said and did should be geared to carrying on his ministry. By the way his followers lived their lives; this crucified leader lived and functioned in the world. In this situation, if the historical Jesus healed "the sick and those disturbed by unclean spirits," then his disciples were expected to do the same.
The author of Revelation suffers because of this concept of ministry. "I found myself (in exile) on the island called Patmos because I proclaimed God's word and gave testimony to Jesus." The writer isn't banished to this remote, insignificant piece of real estate because of the color of his eyes or his politics. He carries on Jesus' work, so he encounters the same opposition which tried to destroy Jesus.
That appears to be why he's granted the vision of Jesus he describes in this passage and hears the words all imitators of Jesus long to hear, "Do not be afraid. I am the first and the last, the one who lives. Once I was dead, but now am alive forever and ever. I hold the keys to death and the netherworld." Today's Christians would have an easier row to hoe if they could share in such an intimate experience of Jesus at least once a week.
The truth is that most of the time we're carrying on Jesus' ministry, we feel like Thomas felt late Easter Sunday night. We only hear from others that Jesus is alive among us. Considering the pain involved in imitating Jesus, we'd prefer to have a more person, tangible encounter with him.
Respecting such a longing, John both describes Thomas' experience a week later, and also has the risen Jesus say something for the benefit of those who weren't in that locked room on either Sunday night. "Have you come to believe because you have seen me? Blessed are those who have not seen and have believed."
We're obviously expected to apply this last statement to ourselves, we who live 20 centuries after Jesus' historical ministry. Yet, the field of those unseeing believers is significantly broader than we sometimes imagine. It includes not only ourselves and most of our faith predecessors, but four people we normally don't put in that category: the four evangelists.
Scripture scholars tell us that none of our gospel writers ever encountered the historical Jesus. Each experienced only the risen Jesus. Unlike the author of Revelation, they never mention any special visions of Jesus intersecting their daily lives. They, like us, had to surface Jesus in their imitation of Jesus.
John deliberately puts his Thomas episode in the context of Jesus' command to forgive. No other action helps us come face to face with the dying/rising Jesus in our midst. And it's also the most dying/rising imitation of Jesus we'll ever take part in.