The next day he saw Jesus coming toward him, and said, "Behold, the Lamb of God, who takes away the sin of the world! This is he of whom I said, 'After me comes a man who ranks before me, for he was before me.' I myself did not know him; but for this I came baptizing with water, that he might be revealed to Israel." And John bore witness, "I saw the Spirit descend as a dove from heaven, and it remained on him. I myself did not know him; but he who sent me to baptize with water said to me, 'He on whom you see the Spirit descend and remain, this is he who baptizes with the Holy Spirit.' And I have seen and have borne witness that this is the Son of God." John 1:29–34 (RSV)
'The Lamb of God, who takes away the sin of the world!' Speaking by the Holy Spirit, John does more than announce Jesus; he proclaims God's purpose through Jesus.
Every day in the Temple, all manner of animals were sacrificed for sin. These sacrifices were repeated as often as a need for people could not shed the sin that clung to them.
The sacrifice of all the creatures in the world would fail to undo the power of sin. We could make a burnt offering of all created things, and sin would persist. Humans are trapped in sin's power. We cannot free ourselves.
Jesus has come as the Lamb of God, whose perfect sacrifice will destroy the power of sin and death. Jesus is our Passover Lamb whose blood turns death from our door. John proclaims the truth, Jesus is the Lamb of God. Jesus is the one who will do what we could not begin to do.
Our Lenten discipline follows the Lamb as He journeys to the cross. Unlike every sacrificed animal before His coming, Jesus' sacrifice makes perfect atonement for all. He truly is the Lamb of God.