Q. How did John the Baptist know that Jesus was “the Lamb of God, which taketh the sin of the world” if, at that moment, the Holy Spirit hadn’t revealed to him that Jesus was the Messiah? “The next day, John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world” (John 1:29 KJV). “And I knew him not: but he that sent me to baptize with water, the same said unto me, Upon whom thou shalt see the Spirit descending, and remaining on him, the same is he which baptizeth with the Holy Ghost” (John 1:33 KJV).
These events are related out of chronological sequence in the Gospel of John for purposes of storytelling. Here they are in chronological sequence:
- When God sends John to baptize, he tells him, “The man on whom you see the Spirit come down and remain is the one who will baptize with the Holy Spirit” (verse 33). God does not tell John specifically who this man is. The descent of the Spirit is the sign that will identify him.
- John begins to baptize people without knowing specifically who the Messiah is (verse 31, “I knew him not”).
- John tells the Pharisees that he is not the Messiah himself, but the Messiah is coming (verses 24–27).
- John sees Jesus coming toward him (verse 29a).
- John sees the Spirit come down from heaven as a dove and remain on Jesus (verse 32).
- Because of this, John says, “Behold, the Lamb of God, who takes away the sin of the world!” (verse 29b).
- John tells the crowds that Jesus is the person he said was coming (verse 30) and testifies that Jesus is the Messiah (verse 34).
I hope this helps clarify the sequence of events. John knew that Jesus was the Lamb of God, and said so, because he had just seen the Spirit descend on him.
Good Question 