Catechism of the Catholic Church
a and d. Para. 565: From the beginning of his public life, at his baptism, Jesus is the "Servant," wholly consecrated to the redemptive work that he will accomplish by the "baptism" of his Passion.
Para. 536: 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" (Jn 1:29; cf. Isa 53:12). Already he is anticipating the "baptism" of his bloody death (cf. Mk 10:38; Lk 12:50).