WCF 14.1.
The grace of faith, whereby the elect are enabled to believe to the saving of their souls, (Heb. 10:39) is the work of the Spirit of Christ in their hearts, (2 Cor. 4:13, Eph. 1:17–19, Eph. 2:8) and is ordinarily wrought by the ministry of the Word, (Rom. 10:14,17) by which also, and by the administration of the sacraments, and prayer, it is increased and strengthened. (1 Pet. 2:2, Acts 20:32, Rom. 4:11, Luke 17:5, Rom. 1:16–17)