John the Baptist saw Jesus coming toward him and said, “Behold, the Lamb of God, who takes away the sin of the world. He is the one of whom I said, ‘A man is coming after me who ranks ahead of me
because he existed before me.’ I did not know him, but the reason why I came baptizing with water was that he might be made known to Israel.” John testified further, saying, “I saw the Spirit come down like a dove from heaven and remain upon him. I did not know him, but the one who sent me to baptize with water told me, ‘On whomever you see the Spirit come down and remain, he is the one who will baptize with the Holy Spirit.’ Now I have seen and testified that he is the Son of God.” [John 1:29-34]
John bears witness not only that Jesus is the Messiah but that he will redeem the world from sin by his violent death. The Baptist’s testimony is portrayed as a model of the witness that Christians should bear to what they have seen and experienced through their belief in Jesus Christ: “All Christians by the example of their lives and the witness of the word, wherever they live, have an obligation to manifest the new man which they put on in Baptism, and to reveal the power of the Holy Spirit by whom they were strengthened at Confirmation, so that others, seeing their good works, might glorify the Father and more perfectly perceive the true meaning of human life and the universal solidarity of making” (Vatican II, Ad gentes, 11).
In calling Jesus the “Lamb of God” (v. 29), John alludes to Christ’s redemptive sacrifice. Isaiah compared the sufferings of the Servant, the Messiah, with the offering of a lamb (see Is 53:7). Moreover, at the time of the Exodus the blood of the Passover lamb, smeared on the doorposts of houses, kept the first-born of Israel safe from death (see Ex 12:6-7).
After Jesus’ death and resurrection, his disciples recognize him to be the true Passover Lamb: before receiving Christ in Holy Communion, that is, when about to share in the “marriage supper of the Lamb,” they make this act of faith.
When John the Baptist says that Jesus “was before me” (v. 30) he acknowledges Jesus’ divinity. As St Gregory puts it, it is as if he were saying: “Although I was born before him, he is not limited by the ties of his birth; for although he is born of his mother in time, he was generated by his Father outside of time” (Homiliae in Evangelia, 7).
The witness borne by John at Jesus’ baptism also reveals the mystery of the Blessed Trinity (see vv. 32-34. The dove is the symbol of the Holy Spirit, who hovered over the face of the waters at the dawn of creation (see Gen 1:2).