WLC Q.73: How doth faith justify a sinner in the sight of God?
Faith justifies a sinner in the sight of God, not because of those other graces which do always accompany it, or of good works that are the fruits of it, (Gal. 3:11, Rom. 3:28) nor as if the grace of faith, or any act thereof, were imputed to him for his justification; (Rom. 4:5, Rom. 10:10) but only as it is an instrument by which he receiveth and applieth Christ and his righteousness. (John 1:12, Phil. 3:9, Gal. 2:16)