The next day John saw Jesus coming toward him, and said, “Behold! The Lamb of God who takes away the sin of the world!” (John 1:29)
The “next day” is the day after John the Baptist had a set-to with Pharisees and Jewish leaders at the river Jordan. It was also some time after John baptized Jesus. Now John sees Jesus coming his way again, and he identifies him publicly: “Behold! The Lamb of God who takes away the sin of the world.”
Though John preached a “baptism of repentance for the forgiveness of sin” (Mark 1:4, Luke 3:3 NIV) it could not itself take away sin, and was never intended to. John’s role was to prepare the way of the Lord, and the baptism he offered was to prepare the people to receive the one to come who would bring forgiveness. John did not know who this one, not until he came to be baptized by John. It was by this baptism that the messianic identity was revealed, and John gives solemn witness to it:
Then John gave this testimony: “I saw the Spirit come down from heaven as a dove and remain on him. And I myself did not know him, but the one who sent me to baptize with water told me, ‘The man on whom you see the Spirit come down and remain is the one who will baptize with the Holy Spirit.’ I have seen and I testify that this is God's Chosen One.” (John 1:32-34 NIV)“Behold!” John says. He is arresting the attention of his listeners, giving them a new focus, inviting them into a new revelation.
“The Lamb of God who takes away the sin of the world.” This is a sacrificial lamb, a pure and spotless lamb, a lamb that takes away sin. Jesus came to John to be baptized, though he had no sin of his own to confess and nothing to repent of. But in the humility of baptism, he identified with the people who very much needed to have their sin taken away. And submitting to those baptismal waters, he foreshadowed the death, burial and resurrection by which he would deal with sin once and for all. The Lamb of God takes away the sin of the whole world and not just that of Israel.
Christian baptism mirrors the baptism of Jesus. In his baptism, Jesus identifies with us. In our baptism, we are identified with him. In his baptism, Jesus’ death, burial and resurrection are prefigured. In our baptism, we are immersed in his death, burial and resurrection. In his baptism, Jesus is revealed as the Lamb of God who takes away the sin of the world. In our baptism, we are revealed as those whose sin is taken away. Behold!