The Gospel of the Second Sunday of Advent concerns St. John the Baptist. You can read many fine homilies on this topic on the web including, of course, the Holy Father's. I want to provide a quick insight by referring once again to the book by Ignatius Press "The Sunday Sermons of the Great Fathers: A Manual of Preaching, Spiritual Reading and Meditation."
I'm doing this because so many Catholics and Christians in general have lost touch with the fathers of the Church, the very people who took over the mantle when Jesus resurrected and preached the Gospel, forming the body of the newborn Church. I think that it can only strengthen and affirm faith to know that people were preaching and teaching about the same things nearly two thousand years ago as they are today, with continuity ALL the way through.
Reading the sermons for this second week in Advent, and the summary of discussion provided by St. Thomas Aquinas in his work the Catena Aurea, those who preached were pondering a mystery about St. John the Baptist. They noted that John had recognized Christ as the Messiah, baptized him himself, and witnessed the Holy Spirit descend on Jesus while hearing the voice of God make his acknowledgement and declaration of Jesus as Son. Yet they are puzzled when John, who is later imprisoned, sends his own disciples to Jesus to inquire, "Art thou he that art to come; or look we for another?" Many of the sermons and writings are in discussion of what this means.
What is beautiful to read in this precious collection of sermons is that there is never a question of faith, but the birth and growing pangs of understanding. The sermon authors, some of whom lived only a few hundred years after Christ, are trying to put themselves in the frame of reference of understanding what was being said and what it meant. They never doubted the truth of what was said, and this continuity has been complete throughout the Catholic Church history. But as I said, it is like having growing pangs, where the more they embrace the Gospel the more they strive to understand the fullness and sweetness of each word. And so they were puzzled by the words of John the Baptist and discussed among themselves several interpretations.
The meaning that you can discern from these words is that even as John the Baptist recognized Jesus as the Messiah, no one knew the fullness of what the Messiah would "do." With the great heritage of priest-kings, the obvious example being David from whom Jesus descended through both Mary's lineage and through his stepfather Joseph's lineage, of course many - virtually all - people who lived in the time of Jesus expected a political and military capable Messiah. So as John the Baptist is imprisoned he wonders what Jesus will "do." John the Baptist was not at all expressing any lack of faith. He just simply, like the rest of the people of the time, did not understand what day to day actions the Messiah would take. John was not doubting that Jesus was the Messiah, but he wondered if he should look elsewhere for the action that he thought would take place with his imprisonment. No one human, even as blessed at John the Baptist, could predict or understand how Jesus would spend his several years of public ministry resulting in the New Covenant. Even those who were well versed in the prophecies of the Old Testament writings about the Messiah, about how he will be persecuted, put to death and so forth, had no reason to believe that this would take place WITHOUT JESUS EVER DRAWING A SWORD. The dire predictions of the outcome of the Messiah made perfect sense because virtually everyone assumed that Jesus would lead a rebellion of some sort, and the outcome of that would be disbelief and being put to death. No one understood how Jesus would revolutionize both Judaism, in the sense of heralding the New Covenant to replace the Old Covenant between God and man and reach out to the pagan gentiles, through the Apostles and disciples after his resurrection, all without taking any political or military action.
So when John the Baptist was imprisoned he obviously thought this would be a watershed moment for the Messiah to act. His sending of his disciples was to try to find out what Jesus would "do."
Now you can better understand both what John was asking, and how Jesus responded. Jesus responded by having John's disciples "observe him at work for a day," to put it in modern terminology. Jesus told the disciples to watch him and report back to John. So the disciples watched Jesus perform miracles of healing: And answering, he said to them: "Go and relate to John what you have heard and seen: the blind see, the lame walk, the lepers are made clean, the deaf hear, the dead rise again, to the poor the gospel is preached. And blessed is he whosoever shall not be scandalized in me." (Luke 7:18-27).
In other words the disciples were observing "how Jesus intended to spend his time," again putting this into modern wording. Jesus was planning to heal through miracles, preach the gospel, and eventually do something that will challenge everyone's notion of scandal. There is the obvious hint to his fate and to John's with the comment "the dead rise again." This was Jesus' way of letting John know that Jesus is not there to raise an army of angels or men to storm prisons or to save lives through the force of arms.
So in this second Sunday week of Advent it is very enlightening to ponder that even the man who was related to Jesus, who heralded his coming, who heard the very voice of God and saw the Holy Spirit as a dove descend still had no clue as to what the Messiah would bring to the world and how he would do it. Part of recapturing the beauty of Advent and one's faith is to fully savor the total uniqueness of Jesus as Son of God, who brought what even the blessed people closest to him could not understand, even as they witnessed it. The heavens genuinely opened and the world changed and was redeemed when Jesus Christ came to bring the New Covenant. And only God could have the vision, the all-knowing, to bring this into being in a way that is so straightforward and yet so mysterious and new to those who actually stood there in their sandals, observed, and partook in this redemption of the world.