Christ instituted two rites that his followers were to observe: baptism, a once-for-all rite of initiation (Matt. 28:19; Gal. 3:27), and the Lord’s Supper, a regular rite of remembrance (1 Cor. 11:23-26). These are called “sacraments” in the Western church, “mysteries” in the Eastern Orthodox church, and “ordinances” by some Protestants who see the other two words as tainted with unhelpful associations. Scripture has no category-word for these two rites and their Old Testament counterparts, namely circumcision of males as a rite of initiation (Gen. 17:9-14, 23-27) and the annual Passover as a rite of remembrance (Exod. 12:1-27). Biblical teaching, however, warrants classifying them all together as signs and seals of a covenant relationship with God.

Sacrament is from the Latin word sacramentum, meaning a holy rite in general and in particular a soldier’s sacred oath of allegiance. Study of the rites themselves yields the concept of a sacrament as a ritual action instituted by Christ in which signs perceived through the senses set forth to us the grace of God in Christ and the blessings of his covenant. They communicate, seal, and confirm possession of those blessings to believers, who by responsively receiving the sacraments give expression to their faith and allegiance to God. The effect of receiving the sacraments is “to put a visible difference between those that belong unto the church and the rest of the world, and solemnly to engage them to the service of God in Christ, according to his word” (Westminster Confession XXVII.1).

It was a medieval mistake to classify as sacraments five more rites (confirmation, penance, marriage, ordination, and extreme unction). In addition to their not being seals of a covenant relationship with God, they “have not like nature of sacraments with Baptism and the Lord’s Supper, for that they have not any visible sign or ceremony ordained of God” (Thirty-Nine Articles XXV).

The sacraments are rightly viewed as means of grace, for God makes them means to faith, using them to strengthen faith’s confidence in his promises and to call forth acts of faith for receiving the good gifts signified. The efficacy of the sacraments to this end resides not in the faith or virtue of the minister but in the faithfulness of God, who, having given the signs, is now pleased to use them. Knowing this, Christ and the apostles not only speak of the sign as if it were the thing signified but speak too as if receiving the former is the same as receiving the latter (e.g., Matt. 26:26-28; 1 Cor. 10:15-21; 1 Pet. 3:21-22). As the preaching of the Word makes the gospel audible, so the sacraments make it visible, and God stirs up faith by both means.

Sacraments strengthen faith by correlating Christian beliefs with the testimony of our senses. The Heidelberg Catechism illustrates this in its answer to Question 75. The key words are as sure as.

Christ has commanded me... to eat of this broken bread and to drink of this cup in memory of him, and therewith has given assurance: first, that his body was... broken on the cross for me, and his blood shed for me, as sure as I see with my eyes the bread... broken for me and the cup communicated to me; and, further, that with his crucified body and shed blood he himself feeds and nourishes my soul to eternal life, as sure as I take and taste the bread and cup... which are given me as sure tokens of the body and blood of Christ.

Sacraments function as means of grace on the principle that, literally, seeing is (i.e., leads to) believing.