What does Matthew 11:3 mean?
John the Baptist has been in prison for as long as a year. Chapter 14 will reveal additional details as to why he was imprisoned. He had declared that Herod's choice to divorce his own wife and marry his brother's wife was not lawful. In retaliation, Herod had him arrested and imprisoned at a fortress called Machaerus, east of the Dead Sea.The gospels make it clear that John was more than just a teacher. He was the fulfilment of God's prophecy in Isaiah 40:3 about a man who would come to "prepare the way of the Lord." John did this by calling Israel to repent because the kingdom of heaven was near. He introduced Israel to Jesus as the Messiah.
The question being posed here suggests John was grappling with doubt. He has heard about what Jesus has been doing, and he has sent his disciples to Jesus with a question: Are you the one who was to come, or should we look for someone else? In short, John the Baptist was asking if Jesus was really the Messiah. It's also possible that John is asking this question rhetorically—that his deeper meaning is something like saying, "Jesus, what are you waiting for?"
John preached that those who failed to "produce good fruit" would be "cut down and thrown into the fire" (Matthew 3:10). He said the Messiah was coming to gather the wheat into His barn and burn up the chaff with unquenchable fire. Scholars suggest John's expectations for the Messiah didn't match up with Jesus' early ministry. This was a common response of people who had been raised to expect a David-like figure who would immediately conquer. Scripture shows that almost nobody understood that Jesus had come to demonstrate power before dying for the sins of the world, and then to be resurrected from the dead. Judgment would come for all who rejected the Messiah, but it would come later.
John had heard about Jesus' preaching and His miracles of healing and casting out demons. He had not heard anything about Jesus bringing judgment on Israel so far. Perhaps John was waiting even for Herod to be judged by the Messiah so they he could be released from prison.