John the Baptist met & knew Jesus several times: before birth, while baptizing Jesus, etc… (besides being Jesus’ cousin) and yet John had to be assured once again after he was arrested by Herod. What happened to make him doubt while he was in prison?
From the Biblical accounts of their lives it’s hard to believe that John the Baptist had doubts about who Jesus really was, and yet his question in Matt. 11:2-3 makes it appear that he did. This is one of those cases where a little background knowledge is helpful. In the Lord’s time there was a religious group called the Essenes. Josephus called them the third major religious sect after the Pharisees and the Saduccees. We know them as the source of the Dead Sea Scrolls. They misunderstood messianic prophecy and believed there would be 2 messiahs instead of two visits by the same one. They called one Son of Joseph after Jacob’s 11th son. He would be the suffering servant who would die for the people. The other would be a conquering King who they named Son of David.
According to tradition, John spent time with the Essenes. I think he knew of this belief and wanted to set the record straight. The question he sent his disciples to ask could be translated from the Greek as, “Are you the (only) one who was to come, or should we (also) expect someone else?”
In His response, the Lord reminded them of miracles He had performed (Matt. 11:4-5). The Essenes believed some of these miracles would be performed by “Son of Joseph” and others would be performed by “Son of David.” In effect, by pointing to the miracles of both Jesus was saying, “I am the only one.”
John didn’t have any doubt. He sent his disciples to Jesus to remove their doubts.