Behold the Lamb of God

John the Baptist was still preparing people at the Jordan River for the coming of the Messiah, yet he had already baptized Jesus and now Jesus walking by ready to begin His mission. John turns to two of his disciples and says something very remarkable, "Behold the Lamb of God." He said this because he knew that Jesus would lay down His life as the Passover Lamb and die for the sins of the world. He told this to his disciples because they must follow Jesus now, John`s work has come to an end. He was baptizing people to prepare them for the coming of the Messiah, and now He was baptized and is walking in their midst. The two disciples leave John to follow Jesus.

Link: https://bible-history.com/new-testament/jesus-begins-his-work