The Heidelberg Catechism, This Lord's Day week 16

Q40: Why was it necessary for Christ to suffer "death"?

A40: Because the justice and truth [1] of God required that satisfaction for our sins could be made in no other way than by the death of the Son of God.[2]
1. Gen. 2:172. Heb. 2:9; Rom. 6:23

Q41: Why was He "buried"?

A41: To show thereby that He was really dead.[1]
1. Matt. 27:59-602. John 19:38-42; Acts 13:29

Q42: Since, then, Christ died for us, why must we also die?

A42: Our death is not a satisfaction for our sin, but only a dying to sin and an entering into eternal life.[1]
1. John 5:24; Phil. 1:23; Rom. 7:24-25

Q43: What further benefit do we receive from the sacrifice and death of Christ on the cross?

A43: That by His power our old man is with Him crucified, slain and buried;[1] so that the evil lusts of the flesh may no more reign in us,[2] but that we may offer ourselves unto Him a sacrifice of thanksgiving.[3]
1. Rom. 6:6-8; Col. 2:122. Rom. 6:123. Rom. 12:1; II Cor. 5:15

Q44: Why is it added: "He descended into hell"?

A44: That in my greatest temptations I may be assured that Christ my Lord, by His inexpressible anguish, pains and terrors, which He suffered in His soul on the cross and before, has redeemed me from the anguish and torment of hell.[1]
1. Isa. 53:10; Matt. 27:46; Psa. 18:5; 116:3