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.