From the Shorter Catechism

Q. 91. How do the Sacraments become effectual means of salvation?

A. The Sacraments become effectual means of salvation, not from any virtue in them, or in him that doth administer them; but only by the blessing of Christ, and the working of his Spirit in them that by faith receive them. 1 Pet. 3:21; Matt. 3:11; 1 Cor. 3:6-7; 1 Cor. 12:13.