I. The grace of faith, whereby the elect are enabled to believe to the saving of their souls, is the work of the Spirit of Christ in their hearts; and is ordinarily wrought by the ministry of the Word: by which also, and by the administration of the sacraments, and prayer, it is increased and strengthened.
II. By this faith, a Christian believeth to be true whatesoever is revealed in the Word, for the authority of god himself speaking therein; and acteth differently, upon that which each particular passage thereof containeth; yielding obedience to the commands, trembling at the threatenings, and embracing the promises of God for this life, and that which is to come. But the principle acts of saving faith are, accepting, receiving, and resting upon Christ alone for justification, sanctification, and eternal life, by virtue of the covenant of grace.
III. This faith is different in degrees, weak or strong; may be often and many ways assailed and weakened, but gets the victory; growing up in many to the attainment of a full assurance through Christ, who is both the author and finisher of our faith.—Westminster Confession of Faith (1646).