John 1:7, 19-23, 35-37

He came as a witness, to bear witness about the light, that all might believe through him.

And this is the testimony of John, when the Jews sent priests and Levites from Jerusalem to ask him, “Who are you?” He confessed, and did not deny, but confessed, “I am not the Christ.” And they asked him, “What then? Are you Elijah?” He said, “I am not.” “Are you the Prophet?” And he answered, “No.” So they said to him, “Who are you? We need to give an answer to those who sent us. What do you say about yourself?” He said, “I am the voice of one crying out in the wilderness, ‘Make straight the way of the Lord,’ as the prophet Isaiah said.”

The next day again John was standing with two of his disciples, and he looked at Jesus as he walked by and said, “Behold, the Lamb of God!” The two disciples heard him say this, and they followed Jesus.