Remember from Matthew 3:4 that John wore camel skins and ate locust. He was a rough looking individual and when they ask him who are you. He says quickly, I am not the messiah. It’s interesting that the pharisees did not have a problem assuming this wild and rough looking man in the wilderness was the promised messiah, but refused to accept Jesus, who could come into the synagogues and teach better than any of them as the messiah.
They go through the typical assumptions that show up when they see a prophet. Are you Elijah? Are you the Prophet (Deuteronomy 18:15) John quotes from Isaiah 40:3 saying that he is the one sent to announce the coming of the Lord. Well that can’t go back and tell their leaders this man never really told us anything. So they ask Why do you baptize? This is when John tells them that there is one among them that they don’t recognize. Jesus has been teaching in the synagogues and these pharisees are out in the wilderness looking for him.
Now notice his response. He says he baptizes with water but that isn’t nothing compared to the one I am proclaiming. I’m not even worthy to untie his sandal. A disciple of a teacher would do many things for his teacher but he would not untie his shoes that would be a servants job. What John is stating is even though he has a large group of followers and they respect and listen to his teaching, He is not even worthy to be a slave of Jesus. We should all learn from John. We are not worthy of anything Jesus gives us, but He loves us so much He asks the Father to accept us as adopted sons through his death.