Then Jesus came from Galilee to the Jordan to be baptized by John. 14But John tried to deter him, saying, "I need to be baptized by you, and do you come to me?" Jesus replied, "Let it be so now; it is proper for us to do this to fulfill all righteousness." Then John consented.
As soon as Jesus was baptized, he went up out of the water. At that moment heaven was opened, and he saw the Spirit of God descending like a dove and lighting on him. And a voice from heaven said, "This is my Son, whom I love; with him I am well pleased. (Mt 3,13-17)
The Baptism in the Jordan is first of all a mystery of light. Here, as Christ descends into the waters, the innocent one who became “sin” for our sake (cf. 2Cor 5:21), the heavens open wide and the voice of the Father declares him the beloved Son (cf. Mt 3:17 and parallels), while the Spirit descends on him to invest him with the mission which he is to carry out.