John the Baptist was surprised that Jesus was asking to be baptized by him. John had already declared himself unworthy to unloose the latchet of the His shoes, and now Jesus was asking him to baptism Him (Luke 3:16).
We are often surprised by the idea that the Lord could use us. Who are we to proclaim the unsearchable riches of God. It is easy to disqualify ourselves. Jesus told John that he had to do it to fulfill all righteousness.
As wonderful as it may seem, the Lord has chosen to use us. God's Word could not have been fulfilled without John's cooperation. The Lord works through men.
We can do nothing by ourselves, but the Lord will do nothing by Himself (John 15:5; Ephesians 3:20). A lack of understanding this has caused many people to miss God's blessings. We pray and desire God's best, but wait on Him to move independently. There are things that we must do to fulfill the righteousness of God in our lives.
John was not seeking to exalt himself, but his failure to baptize Jesus would not have been an act of humility. It would have been stupidity. It takes great humility to recognize the call of God on our life and let Him use us.