Saint John the Baptist, was a preacher during the time of Jesus, who lead a movement of baptism at the Jordan River. He notably is the one who recognizes Jesus as the Messiah and baptizes him at the river. The baptism marks the beginning of Jesus’ ministry. Here we see John standing on the rocks of the river with an angel above holding a scallop shell, a typical symbol of baptism.
The Gospels of Mark, Matthew and Luke all tell the story of Jesus coming to John in Judea to be baptized, “When all the people were being baptized, Jesus was baptized too. And as he was praying, heaven was opened and the Holy Spirit descended on him in bodily form like a dove. And a voice came from heaven: “You are my Son, whom I love; with you I am well pleased” Luke 3:21-22.
The Gospel of John does not record John’s baptizing Jesus, but does introduce Jesus to his disciples as the Lamb of God, "Behold the Lamb of God who takes away the sin of the world" John 1:29. We see in the bottom of the window a lamb holding a Christian banner, a typical symbol of the Lamb of God.