The Heidelberg Catechism (1563):
40. Why did Christ have to go all the way to death? Because God’s justice and truth demand it: only the death of God’s Son could pay for our sin.
41. Why was he “buried”? His burial testifies that he really died.
42. Since Christ has died for us, why do we still have to die? Our death does not pay the debt of our sins. Rather, it puts an end to our sinning and is our entrance into eternal life.
43. What further advantage do we receive from Christ’s sacrifice and death on the cross? Through Christ’s death our old selves are crucified, put to death, and buried with him, so that the evil desires of the flesh may no longer rule us, but that instead we may dedicate ourselves as an offering of gratitude to him.