Catechism of the Catholic Church

The baptism of Jesus is on his part the acceptance and inauguration of his mission as God's suffering Servant. He allows himself to be numbered among sinners; he is already "the Lamb of God, who takes away the sin of the world." Already he is anticipating the "baptism" of his bloody death. Already he is coming to "fulfill all righteousness," that is, he is submitting himself entirely to his Father's will: out of love he consents to this baptism of death for the remission of our sins. The Father's voice responds to the Son's acceptance, proclaiming his entire delight in his Son. The Spirit whom Jesus possessed in fullness from his conception comes to "rest on him." Jesus will be the source of the Spirit for all mankind. At his baptism "the heavens were opened"-the heavens that Adam's sin had closed-and the waters were sanctified by the descent of Jesus and the Spirit, a prelude to the new creation. (606, 1224, 444, 727, 739)