For God so loved the world that he gave his only Son,
so that everyone who believes in him might not perish
but might have eternal life.
-- Jn 3:13-17
Jesus accepted Peter's profession of faith, which acknowledged him to be the Messiah, by announcing the imminent Passion of the Son of Man. He unveiled the authentic content of his messianic kingship both in the transcendent identity of the Son of Man "who came down from heaven", and in his redemptive mission as the suffering Servant: "The Son of Man came not to be served but to serve, and to give his life as a ransom for many." Hence the true meaning of his kingship is revealed only when he is raised high on the cross. Only after his Resurrection will Peter be able to proclaim Jesus' messianic kingship to the People of God: "Let all the house of Israel therefore know assuredly that God has made him both Lord and Christ, this Jesus whom you crucified."
-- CCC 440
The Word became flesh so that thus we might know God's love: "In this the love of God was made manifest among us, that God sent his only Son into the world, so that we might live through him." "For God so loved the world that he gave his only Son, that whoever believes in him should not perish but have eternal life."
-- CCC 458
(See also CCC 423, 661, 219, 444.)
Art: Crocifissione, Santa Croce, Firenze.