How are the means of grace made effectual? How do they work? They do not work out of themselves (ex opere operato), as the Roman Catholic Church insists. Rather, they work by the Spirit of God in the hearts of the elect through faith. As Westminster Shorter Catechism 91 explains,
The sacraments become effectual means of salvation, not from any virtue in them, or in him that does administer them; but only by the blessing of Christ, and the working of his Spirit in them that by faith receive them.
The members of the Westminster Assembly did not, however, believe that all the means of grace are equally efficacious: “The Spirit of God makes the reading, but especially the preaching, of the word, an effectual means of convincing and converting sinners, and of building them up in holiness and comfort, through faith, unto salvation” (WSC 89). The Reformed theologian Geerhardus Vos gave a rationale for the priority of the Word over the sacraments when he wrote:
If necessary, we can think of Word as a means of grace without sacrament, but it is impossible to think of sacrament as a means of grace without Word. The sacraments depend on Scripture, and the truth of Scripture speaks in and through them.
Likewise, prayer becomes a means of grace only as it is shaped by the truth of Scripture. The Holy Spirit takes the Word and enables believers to pray in accord with God’s will.
If we are to grow in grace, we must acknowledge that God has appointed certain means for that growth. We should approach these means with eager anticipation and childlike reliance on the One who adds His blessing to them, and we must rest content in a right use of them, knowing that God has promised to bless them as we use them with repentant and believing hearts.