I. The Definition and Biblical Nature of True Faith
"True faith is not only a certain knowledge, whereby I hold for truth all that God has revealed to us in his word, but also an assured confidence, which the Holy Ghost works by the gospel in my heart; that not only to others, but to me also, remission of sin, everlasting righteousness, and salvation, are freely given by God, merely of grace, only for the sake of Christ's merits." [Zacharias Ursinus - Commentary on the Heidelberg]
"We shall now have a full definition of faith, if we say that it is a firm and sure knowledge of the divine favor toward us, founded on the truth of a free promise in Christ, and revealed to our minds, and sealed on our hearts, by the Holy Spirit." [John Calvin - Institutes]
"And the general nature of faith is thereby so modified, that it does not pass over into a firm and certain knowing, into an objective holding-for-true, but also includes a heartfelt trust in, an entire surrender to, a personal appropriation of the promises of God, bestowed in the gospel." [Herman Bavinck - Reformed Dogmatics]
"True faith is grounded upon knowledge. Knowledge carries the torch before faith." [Thomas Watson - The Ten Commandments (Modernized)]
II. The Divine Ground and Origin of Saving Faith
"The chief and peculiar instrument of justifying faith is the preaching of the gospel." [Zacharias Ursinus - Commentary on the Heidelberg]
"The author of faith in Jesus Christ is God, whose gift it is, and who works this grace of faith in the soul by his Spirit." [Thomas Vincent - The Shorter Catechism]
"The fides salvifica was again through and through religious. God’s grace in Christ was its object, the testimony of God in his word was its ground, the H. Spirit was its author." [Herman Bavinck - Reformed Dogmatics]
"Hence without the illumination of the Spirit the word has no effect; and hence also it is obvious that faith is something higher than human understanding." [John Calvin - Institutes]
III. Justification by Faith Alone (Sola Fide) as Forensic Imputation
"How art thou righteous before God? Answer. Only by a true faith in Jesus Christ; so that, though my conscience accuse me that I have grossly transgressed all the commands of God, and kept none of them, and am still inclined to all evil; notwithstanding God, without any merit of mine, but only of mere grace, grants and imputes to me the perfect satisfaction, righteousness, and holiness of Christ; even so, as if I never had had, nor committed any sin; yea, as if I had fully accomplished all that obedience which Christ hath accomplished for me; inasmuch as I embrace such benefit with a believing heart."
"We are said to be justified by faith only: 1. Because we are justified by the object of faith alone, that is by the merits of Christ only, without which we can have no righteousness whatever: for we are justified for Christ's sake." [Zacharias Ursinus - Commentary on the Heidelberg]
"From this statement, it appears that those who are justified by faith are justified independent of, nay, in the absence of, the merit of works, because faith receives that righteousness which the Gospel bestows." [John Calvin - Institutes]
"Faith is a saving grace, not by the act of believing, as an act, for then it would save as a work -- whereas we are saved by faith in opposition to all works; but faith is a saving grace, as an instrument apprehending and applying Jesus Christ and his perfect righteousness, whereby alone we are saved." [Thomas Vincent - The Shorter Catechism]
"The righteousness that is the ground of justification is a righteousness of God and not of the human being; it comes to the human being only by a gift of grace; it therefore lies ready before his faith in Christ and has need of no supplementation at all." [Herman Bavinck - Reformed Dogmatics]
IV. Faith as the Instrument, Not the Merit, of Salvation
"so that when we say, we are justified by faith only, the sense is, that it is not by meriting, but only by receiving; as when it is said, This beggar is enriched only by receiving alms, all works and merits are excluded therefrom, yea, even the very acceptance of alms, in as far as it is viewed as a merit." [Zacharias Ursinus - Commentary on the Heidelberg]
"We say that faith justifies not because it merits justification for us by its own worth, but because it is an instrument by which we freely obtain the righteousness of Christ." [John Calvin - Institutes]
"the righteousness of Christ is perfect, and sufficient for our justification; and by faith his righteousness is received and made ours in the account of God: therefore we are justified by faith." [Thomas Vincent - The Shorter Catechism]
"Because faith eyes Christ in every duty —it touches the hem of his garment; and through Christ, both the person and the offering are accepted." [Thomas Watson - The Ten Commandments (Modernized)]
V. The Inherent Certitude of Saving Faith Over Against Doubt
"Having this confidence, he trusts and rejoices in the present grace of God, and from this he thus concludes in reference to future good: since God now loves me, and grants unto me such great blessings, he will also preserve me unto eternal life; because he is unchangeable, and his gifts are without repentance." [Zacharias Ursinus - Commentary on the Heidelberg]
"To have faith is not to fluctuate, to vary, to be carried up and down, to hesitate, remain in suspense, vacillate, in fine, to despair; it is to possess sure certainty and complete security of mind, to have whereon to rest and fix your foot." [John Calvin - Institutes]
"But however one determines it, faith is in its essence always certainty, excluding all doubt, fear, despair." [Herman Bavinck - Reformed Dogmatics]
"He who truly believes, is as sure to go to heaven as if he were in heaven already." [Thomas Watson - The Lord's Prayer]
VI. The Inseparable Link Between Faith, Sanctification, and Good Works
"By no means; for it is impossible that those who are implanted into Christ by a true faith, should not bring forth fruits of thankfulness." "But although it never exists alone, and is always joined with love, by which it works, yet it alone justifies—is the act of embracing and applying to itself the merits of Christ." [Zacharias Ursinus - Commentary on the Heidelberg]
"We dream not of a faith which is devoid of good works, nor of a justification which can exist without them: the only difference is, that while we acknowledge that faith and works are necessarily connected, we, however, place justification in faith, not in works." [John Calvin - Institutes]
"True faith is prolific . It brings forth fruit; ... Faith is full of good works. It believes as if it did not work—and it works as if it did not believe." [Thomas Watson - The Lord's Prayer]
"We are justified only by faith in Christ's righteousness without us, but this justification is always accompanied with Sanctification, in which a righteousness is wrought within us, without which our justification cannot be true. By the same faith whereby our persons are justified our hearts also are purified." [Thomas Vincent - The Shorter Catechism]