The Heidelberg Catechism: Lord's Day 26
69. Question: How does holy baptism signify and seal to you that the one
sacrifice of Christ on the cross benefits you?
Answer: In this way: Christ instituted this outward washing and with it gave the promise that, as surely as water washes away the dirt from the body, so certainly His blood and Spirit wash away the impurity of my soul, that is, all my sins.
 Matt. 28:19.  Matt. 3:11; Mark 16:16; John 1:33; Acts 2:38; Rom. 6:3, 4; I Pet. 3:21.
70. Question: What does it mean to be washed with Christ's blood and Spirit?
Answer: To be washed with Christ's blood means to receive forgiveness of sins from God, through grace, because of Christ's blood, poured out for us in His sacrifice on the cross. To be washed with His Spirit
means to be renewed by the Holy Spirit and sanctified to be members of Christ, so that more and more we become dead to sin and lead a holy and blameless life.
 Ez. 36:25; Zech. 13:1; Eph. 1:7; Heb. 12:24; I Pet. 1:2; Rev. 1:5; 7:14.  John 3:5-8; Rom. 6:4; I Cor. 6:11; Col. 2:11, 12.
71. Question: Where has Christ promised that He will wash us with His blood and Spirit as surely as we are washed with the water of baptism?
Answer: In the institution of baptism, where He says: Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit (Matthew 28:19). He who believes and is baptized will be saved, but he who does not believe will be condemned (Mark 16:16). This promise is repeated
where Scripture calls baptism the washing of regeneration and the washing away of sins (Titus 3:5; Acts 22:16).
The Heidelberg Catechism: Lord's Day 25
65. Question: Since then faith alone makes us share in Christ and all His benefits, where does this faith come from?
Answer: From the Holy Spirit, who works it in our hearts by the preaching of the gospel, and strengthens it by the use of the sacraments.
 John 3:5; I Cor. 2:10-14; Eph. 2:8; Phil. 1:29.  Rom. 10:17; I Pet. 1:23-25.  Matt. 28:19, 20; I Cor. 10:16.
66. Question: What are the sacraments?
Answer: The sacraments are holy, visible signs and seals. They were instituted by God so that by their use He might the more fully declare and seal to us the promise of the gospel. And this is the promise: that God graciously grants us forgiveness of sins and everlasting life because of the one sacrifice of Christ accomplished on the cross.
 Gen. 17:11; Deut. 30:6; Rom. 4:11  Matt. 26:27, 28; Acts 2:38; Heb. 10:10.
67. Question: Are both the Word and the sacraments then intended to focus our faith on the sacrifice of Jesus
Christ on the cross as the only ground of our salvation?
Answer: Yes, indeed. The Holy Spirit teaches us in the gospel and assures us by the sacraments that our entire salvation rests on Christ's one sacrifice for us on the cross.
 Rom. 6:3; I Cor. 11:26; Gal. 3:27.
68. Question: How many sacraments has Christ instituted in the new covenant?
Answer: Two: holy baptism and the holy supper.
 Matt. 28:19, 20; I Cor. 11:23-26.
The Heidelberg Catechism: Lord's Day 20
53. Question: What do you believe concerning the Holy Spirit?
Answer: First, He is, together with the Father and the Son, true and eternal God. Second, He is also given to me, to make me by true faith share in Christ and all His benefits, to comfort me, and to remain with me forever.
 Gen. 1:1, 2; Matt. 28:19; Acts 5:3, 4; I Cor. 3:16.  I Cor. 6:19; II Cor. 1:21, 22; Gal. 4:6; Eph. 1:13.  Gal. 3:14; I Pet. 1:2.  John 15:26; Acts 9:31.  John 14:16, 17; I Pet. 4:14.