Justification is by Grace alone imputed through Faith alone in Christ alone

"It is indeed true that in the sight of men a man is made good or evil by his works; but this being made good or evil only means that the man who is good or evil is pointed out and known as such, as Christ says in Matt. 7 [:20], 'Thus you will know them by their fruits.' All this remains on the surface, however, and very many have been deceived by this outward appearance and have presumed to write and teach concerning good works by which we may be justified without even mentioning faith. They go their way, always being deceived and deceiving [II Tim. 3:13], progressing, indeed, but into a worse state, blind leaders of the blind, wearying themselves with many works and still never attaining to true righteousness [Matt. 15:14]. Of such people Paul says in II Tim. 3 [5, 7], "Holding the form of religion but denying the power of it . . . who will listen to anybody and can never arrive at a knowledge of the truth.'
Whoever, therefore, does not wish to go astray with those blind men must look beyond works, and beyond laws and doctrines about works. Turning his eyes from works, he must look upon the person and ask how he is justified. For the person is justified and saved, not by works or laws, but by the Word of God, that is, by the promise of his grace, and by faith, that glory may remain God's, who saved us not by works of righteousness which we have done [Titus 3:5], but by virtue of his mercy by the word of his grace when we believe [1 Cor. 1:21].
From this it is easy to know how far good works are to be rejected or not, and by what standard all the teachings of men concerning works are to be interpreted. If works are sought after as a means to righteousness, are burdened with this perverse leviathan, and are done under the false impression that through them one is justified, they are made necessary and freedom and faith are destroyed; and this addition to them makes them no longer good but truly damnable works. They are not free, and they blaspheme the grace of God since to justify and to save by faith belongs to the grace of God alone. What the works have no power to do they nevertheless - by a godless presumption through this folly of ours - pretend to do and thus violently force themselves into the office and glory of grace. We do not, therefore, reject good works; on the contrary, we cherish and teach them as much as possible. We do not condemn them for their own sake but on account of this godless addition to them and the perverse idea that righteousness is to be sought through them; for that makes them appear good outwardly, when in truth they are not good. They deceive men and lead them to deceive one another like ravening wolves in sheep's clothing [Matt. 7:15]."
- Martin Luther, The Freedom of a Christian, Pg. 38 - 39