The First Luminous Mystery of the Rosary is the Baptism of Jesus in the Jordan river.
Matthew 3:1-6
In those days John the Baptist appeared, preaching in the desert of Judea [and] saying, “Repent, for the kingdom of heaven is at hand!” It was of him that the prophet Isaiah had spoken when he said: “A voice of one crying out in the desert, ‘Prepare the way of the Lord,
make straight his paths.’” John wore clothing made of camel’s hair and had a leather belt around his waist. His food was locusts and wild honey. At that time Jerusalem, all Judea, and the whole region around the Jordan were going out to him and were being baptized by him in the Jordan River as they acknowledged their sins.
Matthew 3:13-17
Then Jesus came from Galilee to John at the Jordan to be baptized by him. John tried to prevent him, saying, “I need to be baptized by you, and yet you are coming to me?” Jesus said to him in reply, “Allow it now, for thus it is fitting for us to fulfill all righteousness.” Then he allowed him. After Jesus was baptized, he came up from the water and behold, the heavens were opened [for him], and he saw the Spirit of God descending like a dove [and] coming upon him. And a voice came from the heavens, saying, “This is my beloved Son, with whom I am well pleased.”
