Th Importance of Justification by Faith (From the writings of Martin Luther)

"This doctrine [justification by faith] is the head and the cornerstone. It alone begets, nourishes, builds, preserves, and defends the church of God; and without it the church of God cannot exist for one hour…. For no one who does not hold this article – or, to use Paul's expression, this 'sound doctrine' (Titus 2:1) – is able to teach aright in the church or successfully to resist any adversary . . . this is the heel of the Seed that opposes the old serpent and crushes its head. That is why Satan, in turn, cannot but persecute it.""Whoever departs from the article of justification does not know God and is an idolater . . . For when this article has been taken away, nothing remains but error, hypocrisy, godlessness, and idolatry, although it may seem to be the height of truth, worship of God, holiness, etc."
"If the article of justification is lost, all Christian doctrine is lost at the same time. And all the people in the world who do not hold to this justification are either Jews or Turks or papists or heretics; for there is no middle ground between these two righteousness: the active one of the Law and the passive one which comes from Christ. Therefore the man who strays from Christian righteousness must relapse into the active one, that is, since he has lost Christ, he must put his confidence in his own works."
"When the article of justification has fallen, everything has fallen. Therefore it is necessary constantly to inculcate and impress it, as Moses says of his Law (Deut. 6:7); for it cannot be inculcated and urged enough or too much. Indeed, even though we learn it well and hold to it, yet there is no one who apprehends it perfectly or believes it with a full affection and heart. So very trickish is our flesh, fighting as it does against the obedience of the spirit."
"The article of justification and of grace is the most delightful, and it alone makes a person a theologian and makes of a theologian a judge of the earth and of all affairs. Few there are, however, who have thought it through well and who teach it aright."
"Of this article [justification] nothing may be yielded or conceded, though heaven and earth and whatever will not abide, fall to ruin; for 'there is none other name under heaven given among men whereby we must be saved,' says St. Peter (Acts 4:12); 'and with His stripes we are healed' (Is. 53:5). And on this article all that we teach and practice is based, against the pope, the devil, and the world. That is why we must be very certain of this doctrine and not doubt; otherwise all is lost, and the pope and the devil and all things gain the victory over us and are adjudged right."
"The article of justification must be learned diligently. It alone can support us in the face of these countless offenses and can console us in all temptations and persecutions. For we see that it cannot be otherwise: the world is bound to be offended at the doctrine of godliness and to cry out constantly that nothing good comes of it, since 'the natural man receiveth not the things of the Spirit of God, for they are foolishness unto him.' "
"In short, if this article concerning Christ — the doctrine that we are justified and saved through Him alone and consider all apart from Him damned — is not professed, all resistance and restraint are at an end. Then there is, in fact, neither measure nor limit to any heresy and error."
"There is this about the article of grace that if one diligently and sincerely remains loyal to it, it keeps one from falling into heresy and from undertaking anything against Christ or His Christendom. For with it comes the Holy Spirit, who enlightens the heart by it and keeps it in the true, certain understanding, so that it is able precisely and plainly to distinguish and judge all the other articles of faith and forcefully to sustain and defend them."
"The papacy is shaken and shattered nowadays, not through these tumults of the sectaries but through the preaching of the article of justification, which has not only weakened the kingdom of Antichrist but has also till now sustained and defended us against its power."