John the Baptist and Jesus had known each other from childhood. The two were related and grew up together. The language in today's reading seems to suggest that John knew not much of Jesus or at least knew very little about the divinity of Jesus. John knew very well of Jesus as a young man but in term of Jesus' mission, his hidden life and his divinity John knew not much of him. John was torn between the vision he had of Jesus and the uncertainty of the revelation that made his language evasive.
John was the son of the high priest and from childhood John had seen from time to time the lambs were slaughtered at the Alter as the sacrificial lamb. John's father Zachariah probably had explained to him about the two concepts of the Messiah. One is the suffering Messiah and the other is the conquering Messiah. There is only one Messiah but there are two aspects of his mission: a suffering aspect and the conquering aspect. Today we knew that Jesus had fulfilled both roles: the suffering on the cross and the conquering of the cross over sin and death. The idea of the suffering and conquering servant was founded in Isaiah 53. In the Exodus 12 the blood of Passover Lamb spared the Israelites in Egypt from death and freed them from the slavery in the hand of Pharaoh. The blood of Jesus, the true Passover Lamb (1 Cor. 5:7) spared us from death and destruction. We don't know what John had in mind when he introduced Jesus to his disciples as The Lamb of God but we believe that John understood very well the concept of the suffering and conquering of the sacrificial lamb.
The phrase 'there is a lamb of God that takes away the sin of the world' is a problematic. The verb 'take away' is used in the present tense. The present tense is more likely referring the action of the lamb, taking away the sin, which is much more important than date and hour. The time is right now and will be happening in the future. In other words John talked about the mission of the Lamb which began with Jesus and it continues to happen till it is completed in Christ. John firmly believed that Jesus was powerful both in His deeds and in His words because John himself saw the Spirit coming down on Jesus and that meant His actions and words had the power and authority.
I saw the Spirit coming down on him from heaven like a dove and resting on him. 1,32
The Spirit looked like a dove form to rest on Jesus and remained with Jesus all the time. St Luke described that Jesus was full of the Spirit. It is understood in a sense that it is the unity between Jesus and the Spirit. The presence of the Spirit confirmed and authenticated the teaching and the mission of Jesus. This reality was recognized by the crowds when they said to one another:
His teaching made a deep impression on them because, unlike the scribes, he taught them with authority Mark 1,22, Mat 7,29.