Francis Turretin: Justification by faith alone is of the greatest importance

This [doctrine of justification by faith alone] must be handled with the greater care and accuracy as this saving doctrine is of the greatest importance in religion. It is called by Luther “the article of a standing or a falling church.” By other Christians, it is termed the characteristic and basis of Christianity—not without reason—the principal rampart of the Christian religion. This being adulterated or subverted, it is impossible to retain purity of doctrine in other places. Hence Satan in every way has endeavored to corrupt this doctrine in all ages, as has been done especially in the papacy.

-Francis Turretin, "Institutes of Elenctic Theology," 2:633. (Quoted by Morecraft in "Authentic Christianity," vol. 2, p. 954.)

John Robbins: The doctrine of Christ's perfect, extrinsic, objective, imputed righteousness--forensic justification--ended 1,000 years of stagnation

For a thousand years, because of the church's doctrine of justification as an internal grace rather than the objective, external, legal declaration of a sinner's innocence by God, men had looked inside themselves for the grace that merited salvation. The more devout retreated to monasteries and convents to find their salvation in their interior lives. Some sat on poles, some beat their bodies bloody, and some made pilgrimages to "holy" places. The church had lost the message of the Gospel, that men are saved by a righteousness wholly outside of themselves—the righteousness of Christ. By his perfect life, innocent and substitutionary death, and bodily resurrection, Christ had fulfilled the demands of God's law on behalf of all who believed in him. It is to Christ that one must look for salvation, said Luther, not inside oneself. Once the religious subjectivism of the medieval church was eliminated in Protestant countries, the energy consumed by desperately seeking and earning salvation was turned outward, and a thousand years of intellectual, political, social, economic, and religious stagnation ended.

Brian Schwertley: Luke 18:9-14 clearly demonstrates a faith/works antithesis in justification

Christ our Savior speaks in Luke 18:9-14 --

[9] And he spake this parable unto certain which trusted in themselves that they were righteous, and despised others: [10] Two men went up into the temple to pray; the one a Pharisee, and the other a publican. [11] The Pharisee stood and prayed thus with himself, God, I thank thee, that I am not as other men are, extortioners, unjust, adulterers, or even as this publican. [12] I fast twice in the week, I give tithes of all that I possess. [13] And the publican, standing afar off, would not lift up so much as his eyes unto heaven, but smote upon his breast, saying, God be merciful to me a sinner. [14] I tell you, this man went down to his house justified rather than the other: for every one that exalteth himself shall be abased; and he that humbleth himself shall be exalted.

Brian Schwertley comments on the implications of this passage regarding covenantal faithfulness contrasted with self-renouncing faith, with respect to justification:

Note how Jesus (like Paul after Him) contrasts two radically different views of biblical religion. The Pharisee boasts about his covenantal faithfulness; about his own subjective righteousness; about his faithfulness to God’s law. The tax collector, on the other hand, understands that his works merit nothing, that he is a sinner and thus casts himself entirely upon God’s mercy. He understands that he must receive everything from God.

Note also that Christ is discussing two religious Jews who were at the Temple praying. These men were both covenantal sons, not slaves. This means that Jesus condemns a reliance on covenantal faithfulness or keeping the moral law as a means of approaching God in the same manner as Paul, His beloved disciple. Any attempt to circumvent the import of this passage by looking to the “identity markers” theory is refuted in two ways. First, the Pharisee relied on the moral law for righteousness or individual salvation. Second, both men were Jews. Attitudes regarding the status of the Gentiles have nothing to do with this parable. Once again, we see that the faith that justifies is a self-renouncing faith that looks to the righteousness of another. The faith/works antithesis in the sphere of justification that was and is one of the pillars of Lutheranism and the Reformed faith must be maintained. It is thoroughly biblical. (Brian Schwertley, A Refutation of the Auburn Avenue Theology's Rejection of Justification by Faith Alone)

Martin Luther: We are intrinsically sinners and extrinsically justified by God's declaration of the imputation of Christ's righteousness

Martin Luther explains that we are at the same time justified (right with God by His gracious legal declaration) and sinners in ourselves ("Simul Iustus et Peccator"):

The saints are intrinsically always sinners, therefore they are always extrinsically justified; but the hypocrites are intrinsically always righteous, therefore they are extrinsically always sinners….Hence, we are extrinsically righteous in so far as we are righteous not in and from ourselves and not in virtue of our works but only by God ’s regarding us so. For inasmuch as the saints are always aware of their sin and implore God for the merciful gift of his righteousness, they are for this very reason also always reckoned righteous by God. Therefore they are before themselves and in truth unrighteous, but before God they are righteous because he reckons them so on account of this confession of their sin; they are sinners in fact, but by virtue of the reckoning of the merciful God they are righteous. (Martin Luther, Lectures on Romans, 124-125 as quoted by Samuel E. Waldron, “The Meaning of Sola Fide for Luther” in Reformed Baptist Theological Review [Palmdale, CA: January 2004] Vol. 1, No. 1, 100; quoted by Brian Schwertley in his refutation of the Auburn Avenue theology)

Francis Turretin: Justification is of the greatest importance

Francis Turretin explains the importance, biblically and historically, of justification by faith:

The topic concerning Vocation and Faith begets the Topic concerning Justification, which must be handled with the greater care and accuracy as this saving doctrine is of the greatest importance in religion. It is called by Luther, the article of a standing and falling church; by other Christians it is termed the characteristic and basis of Christianity not without reason, the principle rampart of the Christian religion, and, it being adulterated or subverted, it is impossible to retain purity of doctrine in other places. Whence Satan in every way has endeavored to corrupt this doctrine in all ages; as has been done especially in the Papacy: for which reason it is deservedly placed among the primary causes of our Secession from the Roman Church and of the Reformation. (Francis Turretin, Forensic Justification)

Archibald Alexander: Without "Sola Fide," the whole Christian system is lost, echoing Luther

Archibald Alexnader explains the central importance of justification by faith alone within Christian theology:

"How shall a man be just with God?" is surely the most important question which can possibly be conceived. … On some other points error may exist, and yet the state of the person entertaining it may notwithstanding be safe; he may still be in the right way to heaven. But a mistake, as to the method of acceptance with God, must be exceedingly dangerous: it must mislead the inquirer from the way of salvation. Let every man, then, as he regards his own eternal happiness, beware of embracing a false doctrine on this subject. … Wherever, and whenever, justification by faith, has been given up, obscured, or neglected to be preached, then and there, other errors have come in like a flood, and true religion has declined. … [Luther’s] pithy and striking declaration, that it was "the article of a standing or falling church," has often been cited; but another saying of this great reformer, equally pithy and important, is less known. "The doctrine of justification being lost," says he "the whole system of Christian doctrine is lost." (Archibald Alexander, A Treatise on Justification by Faith Alone)

C. Matthew McMahon: Justification by Faith Alone is one of the most important, yet neglected, doctrines

C. Matthew McMahon on the fundamental importance of justification by faith alone:

However, in the sea of doctrine which we are all to be familiar with throughout the Word of God, there may be a doctrine which is more important than any other; one which is the most important of all. Some may vouchsafe for the atonement. I must admit, the atonement is crucial, critical and the crux of saving grace for the believer. But, the importance of a doctrine does not simply fall on the kind of doctrine or the content of the doctrine, but also on the need of the doctrine as well. Eschatology is very important, but not as important as the need to understand the atonement. Today, I believe, as it was in the sixteenth century, the need to regain lost ground in understanding the doctrine of Justification by faith alone has come to the forefront. Most people, even those in Reformed circles, those who claim Luther as a hero, have little to say about justification. I have been a member of solid reformed churches for quite a long time. Yet, I have heard very little about justification by faith alone. I cannot remember a sermon dedicated to the subject. It has been neglected in the school setting, in the home study groups, and in the pulpit. It is a vital doctrine that we cannot do without. Its urgency dictates the difference between one going to heaven and one going to hell. It is of crucial significance and should be rightly understood by those who claim Christ as their banner. If justification is misunderstood, being the pillar upon which the church stands or falls, then what will the rest of our doctrine look like? Will it be a nominal Christianity? Would it be works righteousness? I think it would. To understand that we must be clothed in the righteousness of Christ for safety in the Day of Judgment is of vital import.

As I believe the doctrine of seeking is all but lost in our day, I also believe the doctrine of justification is slowly being forgotten. Friends, without it we are lost. Without understanding it we will not truly perceive the great wonder of the grace of God in Christ. It is my hope that in this section of the website such a glorious truth may be exalted beyond measure, that it may bring a great amount of glory to the one true and living God of the Ages. Let us think rightly about one of the most, if not the most important doctrine in the entire bible, the Doctrine of Justification by Faith alone. (C. Matthew McMahon, Justification by Faith Alone: A Plea for Understanding)

C.H. Spurgeon: The Gospel is unclear without the imputation of Christ's righteousness

C.H. Spurgeon on the imputation of Christ's righteousness:

When we say that the righteousness of Christ is imputed to an believing souls, we do not hold forth an exceptional theory, but we expound a grand truth, which is so consistent with the theory of the fall and the plan of pardon, that it must be maintained in order to make the gospel clear. I think it was this doctrine which Martin Luther called the article of standing or falling of the Church. I find a passage in his works which seems to me to refer to this doctrine rather than to justification by faith. He ought certainly to have said, "Justification by faith is the doctrine of standing or falling of the Church." But in Luther's mind, imputed righteousness we, so interwoven with justification by faith, that he could not see any distinction between the two. And I must confess, in trying to observe a difference, I do not see much. I must give up justification by faith if I give up imputed righteousness. True justification by faith is the surface soil, but then imputed righteousness is the granite rock which lies underneath it; and if you dig down through the great truth of a sinners being justified by faith in Christ, you must, as I believe, inevitably come to the doctrine of the imputed righteousness of Christ as the basis and foundation on which that simple doctrine rests. (C.H. Spurgeon, The Lord Our Righteousness)

John Gill: Justification by the righteousness of Christ is the "essence of the Gospel"

John Gill on the importance of the doctrine of justification:

The doctrine of justification by the righteousness of Christ is a doctrine of great importance; the apostle speaks of it as if the essence of the gospel lay in it; and calls the opposite to it, justification by the works of the law, another gospel; (see Gal. 1:6,7; 3:8), it is a fundamental article of the gospel; some have called it, the "basis" of Christianity; it was the great doctrine of the reformation; what our first reformers made their chief study; and by it cut the sinews of "popery", the antichristian doctrines of penance and purgatory, of pardons and indulgences, of the merit of good works, works of supererogation, &c. Luther used to call it, "articulus stantis vel cedentis ecclesiae" the article of the church, by which it stands or falls; as this is, the church is; if this obtains, the church is in a well settled and prosperous state; but if this loses ground, and is rejected, it is in a ruinous one: if this is a rule to judge by, it may be easily discerned, in what case the church, and interest of religion, now are. This doctrine is the ground and foundation of all solid joy, peace, and comfort, in this life, and hope of eternal glory hereafter. (John Gill, A Body of Doctrinal Divinity: Book 6—Chapter 8: Of Justification)