John could not understand why the greater One would come to the lesser. He had just told the crowds that the One coming after him was so much mightier that he was not worthy to carry His shoes, and that He would baptize "with the Holy Ghost, and with fire" (Matthew 3:11). Now that One came to Jordan "to be baptized of him" (Matthew 3:13). Barnes explains John's thought: it would be more fitting for John to receive Jesus' baptism, the Holy Spirit, and "I am a sinner, and unworthy to administer this to the Messiah." Gill says John objected because of the majesty of Christ's person, who "stood in no need of such an outward ordinance," and because of his own unworthiness. The question is not doubt but holy surprise.

Jesus answered John directly: "Suffer it to be so now: for thus it becometh us to fulfil all righteousness" (Matthew 3:15). John yielded: "Then he suffered him." As Jesus came up out of the water, "the heavens were opened unto him," the Spirit of God descended "like a dove," and a voice from heaven said, "This is my beloved Son, in whom I am well pleased" (Matthew 3:16-17). John's question was answered by Jesus' word, and God Himself testified who Jesus is.

The KJV word "forbad" translates diekoluen, a strong verb that Thayer defines as to hinder or prevent, and that appears only here in the New Testament. Its tense pictures an ongoing attempt, which is why the ESV says John "would have prevented him."

John's baptism was a baptism "unto repentance" for people "confessing their sins" (Matthew 3:6, 11). That is why Jesus' request surprised him. Barnes notes there was no Old Testament command that required Jesus to be baptized, but He chose "to give the sanction of his example" to John's baptism as an ordinance from God. Matthew Henry says Jesus counted it right "to fulfil all righteousness, to own every Divine institution."

This question shows the humility of Jesus. The One who would baptize with the Holy Ghost came to the same baptism as the people "confessing their sins" (Matthew 3:6, 13). Matthew Henry writes, "Christ's gracious condescensions are so surprising, that even the strongest believers at first can hardly believe them."

God Himself then answers the question of who this is. The Spirit descends and the Father speaks: "This is my beloved Son" (Matthew 3:17). Mark and Luke record the baptism and the voice (Mark 1:9-11; Luke 3:21-22), but only Matthew records John's question. The surprise John felt opens the way for God to declare who Jesus is.