“If Christ has not been raised, then our preaching is in vain and your faith is in vain.” The Resurrection above all constitutes the confirmation of all Christ’s works and teachings. All truths, even those most inaccessible to human reason, find their justification if Christ by his Resurrection has given the definitive proof of his divine authority, which he had promised.
Christ’s Resurrection is the fulfilment of the promises both of the Old Testament and of Jesus himself during his earthly life. The phrase “in accordance with the Scriptures” indicates that Christ’s Resurrection fulfilled these predictions.
The truth of Jesus’ divinity is confirmed by his Resurrection. He had said: “When you have lifted up the Son of man, then you will know that I am he.” The Resurrection of the crucified one shows that he was truly “I AM”, the Son of God and God himself. So St. Paul could declare to the Jews: “What God promised to the fathers, this he has fulfilled to us their children by raising Jesus; as also it is written in the second psalm, ‘You are my Son, today I have begotten you.'” Christ’s Resurrection is closely linked to the Incarnation of God’s Son, and is its fulfilment in accordance with God’s eternal plan.
The Paschal mystery has two aspects: by his death, Christ liberates us from sin; by his Resurrection, he opens for us the way to a new life. This new life is above all justification that reinstates us in God’s grace, “so that as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life.” Justification consists in both victory over the death caused by sin and a new participation in grace. It brings about filial adoption so that men become Christ’s brethren, as Jesus himself called his disciples after his Resurrection: “Go and tell my brethren.” We are brethren not by nature, but by the gift of grace, because that adoptive filiation gains us a real share in the life of the only Son, which was fully revealed in his Resurrection.
Finally, Christ’s Resurrection – and the risen Christ himself is the principle and source of our future resurrection: “Christ has been raised from the dead, the first fruits of those who have fallen asleep. . . For as in Adam all die, so also in Christ shall all be made alive.” The risen Christ lives in the hearts of his faithful while they await that fulfilment. In Christ, Christians “have tasted. . . the powers of the age to come” and their lives are swept up by Christ into the heart of divine life, so that they may “live no longer for themselves but for him who for their sake died and was raised.”
From the Catechism of the Catholic Church 651-655