I didn't recognize him, but he who sent me to baptize in water, he said to me, 'On whomever you will see the Spirit descending, and remaining on him, the same is he who baptizes in the Holy Spirit.'

 Something had happened at the baptism of Jesus which had convinced John beyond all doubt that Jesus was the Son of God. As the fathers of the church saw centuries ago, it was something which only the eye of the mind and soul could see. But John saw it and was convinced. 