CATECHISM OF THE CATHOLIC CHURCH
SECOND EDITION

Paragraphs 627–631

627 Christ's death was a real death in that it put an end to his earthly human existence. But because of the union which the person of the Son retained with his body, his was not a mortal corpse like others, for "it was not possible for death to hold him" and therefore "divine power preserved Christ's body from corruption." Both of these statements can be said of Christ: "He was cut off out of the land of the living", and "My flesh will dwell in hope. For you will not abandon my soul to Hades, nor let your Holy One see corruption." Jesus' Resurrection "on the third day" was the sign of this, also because bodily decay was held to begin on the fourth day after death.
628 Baptism, the original and full sign of which is immersion, efficaciously signifies the descent into the tomb by the Christian who dies to sin with Christ in order to live a new life. "We were buried therefore with him by baptism into death, so that as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life."
629 To the benefit of every man, Jesus Christ tasted death (cf. Heb 2:9). It is truly the Son of God made man who died and was buried.
630 During Christ's period in the tomb, his divine person continued to assume both his soul and his body, although they were separated from each other by death. For this reason the dead Christ's body "saw no corruption" (Acts 13:37).
631 Jesus "descended into the lower parts of the earth. He who descended is he who also ascended far above all the heavens." The Apostles' Creed confesses in the same article Christ's descent into hell and his Resurrection from the dead on the third day, because in his Passover it was precisely out of the depths of death that he made life spring forth:

Christ, that Morning Star, who came back from the dead, and shed his peaceful light on all mankind, your Son who lives and reigns for ever and ever. Amen.