29 The next day John saw Jesus coming toward him and said, "Look, the Lamb of God, who takes away the sin of the world! 30 This is the one I meant when I said, 'A man who comes after me has surpassed me because he was before me.' 31 I myself did not know him, but the reason I came baptizing with water was that he might be revealed to Israel."
32 Then John gave this testimony: "I saw the Spirit come down from heaven as a dove and remain on him. 33 I would not have known him, except that the one who sent me to baptize with water told me, 'The man on whom you see the Spirit come down and remain is he who will baptize with the Holy Spirit.' 34 I have seen and I testify that this is the Son of God."
After talking with someone about their sin, and how Jesus is the one that paid the price so they could be set free, describing Him as the 'Lamb of God, who takes away the sin of the world" should make some sense. It is also noteworthy that he was first revealed to Israel. Jesus, was, is, and always will be Jewish. He came not so Jews would have to change their religion. He came so that Jews would have their sins forgiven. They were intimately familiar with the sacrifice of an unblemished lamb that was necessary to cover their sin, the blood of the lamb that made the Angel of Death 'Pass Over' their families, and this is a direct parallel with Christ Himself as the unblemished lamb that would once and for all pay for their sins.