Book 4 of 4 - External Means by which God Invites Us into the Society of Christ and Holds Us Therein
Chapter 14 - The Sacraments
18-20 - Sacraments, generally, in Scripture
18. God has used natural things, and miracles as sacraments, generally, to convey promises or support faith. The tree of life and rainbow; the smoking fire pot (Gen 15:17), Gideon's fleece, and Hezekiah's sundial were miracles.
19. In the sacraments "God leagues Himself with us, and we pledge ourselves to purity and holiness of life." God promises to forgive our sin; we ask Him to do so, and pursue piety.
20. There were different sacraments in the Old Testament, according to God's will: circumcision - Gen 17:10; rites of purification (Lev 11-15) and sacrifice (Lev 1-10). We now have baptism and the Lord's Supper - Matt 28:19; 26:26-28. Laying on hands on ministers of the church could also be called a sacrament.