Charles Spurgeon Commentary John 1:31-33

"And I knew him not; but that he should be made manifest to Israel, for this cause came I baptizing in water. And John bare witness, saying, I have beheld the Spirit descending as a dove out of heaven; and it abode upon him. And I knew him not: but he that sent me to baptize in water, he said unto me, Upon whomsoever thou shalt see the Spirit descending, and abiding upon him, the same is he that baptizeth in the Holy Spirit." — John 1:31-33 (ASV)

But that he should be made manifest to Israel, therefore I have come baptizing with water. And John bare record, saying, I saw the Spirit descending from heaven like a dove, and it remained on him.

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 was not to rely on his own judgment. No doubt he was morally certain that Jesus was the Christ. He had been brought up with him; he knew his mother, he had heard of his wondrous birth; John and Jesus must have often been together. But he was not to use his own judgment in this case, but to wait for the sign from heaven; and until he witnessed it, he did not say a word about it. When he saw the Holy Ghost descend upon him, then he knew that it was indeed he.