The Heidelberg Catechism: Lord's Day 16
40. Question: Why was it necessary for Christ to humble Himself even unto
Answer: Because of the justice and truth of God satisfaction for our sins could be made in no other way than by the death of the Son of God.
 Gen. 2:17.  Rom. 8:3; Phil. 2:8; Heb. 2:9, 14, 15.
41. Question: Why was he buried?
Answer: His burial testified that He had really died.
 Is. 53:9; John 19:38-42; Acts 13:29; I Cor. 15:3,4.
42. Question: Since Christ has died for us, why do we still have to die?
Answer: Our death is not a payment for our sins, but it puts an end to sin and is an entrance into eternal life.
 John 5:24; Phil. 1:21-23; I Thess. 5:9, 10.
43. Question: What further benefit do we receive from Christ's sacrifice and death on the cross?
Answer: Through Christ's death our old nature is crucified, put to death, and buried with Him, so that the evil desires of the flesh may no longer reign in us, but that we may offer ourselves to Him as a sacrifice of thankfulness.
 Rom. 6:5-11; Col. 2:11, 12.  Rom. 6:12-14.  Rom. 12:1; Eph. 5:1, 2.
44. Question: Why is there added: He descended into hell?
Answer: In my greatest sorrows and temptations I may be assured and comforted that my Lord Jesus Christ, by His unspeakable anguish, pain, terror, and agony, which He endured throughout all His sufferings but especially on the cross, has delivered me from the anguish and torment of hell.
 Ps. 18:5, 6; 116:3; Matt. 26:36-46; 27:45, 46; Heb. 5:7-10.  Is. 53.
The Heidelberg Catechism
Lord's Day 1