Book 4 of 4 - External Means by which God Invites Us into the Society of Christ and Holds Us Therein
Chapter 14 - The Sacraments
7-13 - They confirm faith by the Spirit; we profess our faith by them
7. If the wicked can partake of the sacraments, this doesn't make them useless, any less than the wicked rejecting the Gospel preached makes preaching useless. According to Paul, the sacraments "include in them the communicating of Christ" - see Gal 3:27; 1 Cor 12:12-13 - while for the unbeliever they are "empty figures." You can't object that you either have faith or you don't, so sacraments can't help strengthen faith. Luke 17:5; Mark 9:24 both show we should seek a stronger faith.
8. The eunuch in Acts 8:37 received baptism on believing with all his heart, but this didn't mean his faith was fully mature - Eph 4:13. The sacraments are given to grow our faith. God gives us (1) His Word, (2) His sacraments to confirm the Word, and (3) His Spirit to "open our hearts for the Word and sacraments to enter in."
9. The power of the sacraments to confirm faith is not in the sacraments themselves, but in the Spirit, who uses them in this way. "What sight does in our eyes for seeing light... the Holy Spirit [does] in our hearts [to] conceive, sustain, nourish, and establish faith."
10. The Spirit must make us teachable (able to see), for the sacraments as a visible word to affect us.
11. Word and sacrament work equally to confirm our faith. As the Word is sown in us and can only "grow by heavenly blessing..."
12. ... so with the sacraments. The sign of the spiritual reality is included and spoken of AS the reality - Gen 3:22 (tree of life); Eph 2:11-12 (circumcision). This doesn't diminish God's glory, for there is "no power in creatures." God only uses us and sacraments as instruments. The sacraments "set [God's] promises before our eyes to be looked upon, indeed, to be guarantees of them to us." Our trust isn't in the sacraments, but in the promises they display.
13. Some try to say that since the word sacrament comes from the oath a Roman soldier took, that it refers mainly to the outward confession, which sets one apart. This is the secondary meaning - to "attest our confession before men." The main thing is that they "serve our faith before God," pointing to the promises - 2 Cor 6:16; Ezek 37:27.