What good is it, my brothers, if a man claims to have faith but has no deeds? Can such faith save him? Suppose a brother or sister is without clothes and daily food. If one of you says to him, "Go, I wish you well; keep warm and well fed," but does nothing about his physical needs, what good is it? In the same way, faith by itself, if it is not accompanied by action, is dead. But someone will say, "You have faith; I have deeds." Show me your faith without deeds, and I will show you my faith by what I do. --Epistle of James 2: 14-18So the Christian who is consecrated by his faith does good works, but the works do not make him holier or more Christian, for that is the work of faith alone. And if a man were not first a believer and a Christian, all his works would amount to nothing and would be truly wicked and damnable sins.--Martin Luther, The Freedom of a ChristianThe following statements are therefore true: "Good works do not make a good man, but a good man does good works; evil works do not make a wicked man, but a wicked man does evil works." Consequently it is always necessary that the substance or person himself be good before there can be any good works, and that good works follow and proceed from the good person, as Christ also says, "A good tree cannot bear evil fruit, nor can a bad tree bear good fruit" [Matt. 7:18]. It is clear that the fruits do not bear the tree and that the tree does not grow on the fruits, also that, on the contrary, the trees bear the fruits and the fruits grow on the trees. As it is necessary, therefore, that the trees exist before their fruits and the fruits do not make trees either good or bad, but rather as the trees are, so are the fruits they bear; so a man must first be good or wicked before he does a good or wicked work, and his works do not make him good or wicked, but he himself makes his works either good or wicked. --Martin Luther, Works 31:360-361When God rewards my labors, He's merely crowning the works of His hands in my life."--St. AugustineIf anyone says that the righteousness received is not preserved and also not increased before God by good works, but that those works are merely the fruits and signs of justification obtained, but not a cause of its increase, let him be anathema."--Council of Trent, 1563St. Thomas Aquinas' Summa Theologica:Can man without grace and by his own natural powers fulfil the commandments of the Law? Objection 1. It would seem that man without grace, and by his own natural powers, can fulfil the commandments of the Law. For the Apostle says (Rm. 2:14) that "the Gentiles who have not the law, do by nature those things that are of the Law." Now what a man does naturally he can do of himself without grace. Hence a man can fulfil the commandments of the Law without grace.
Objection 2. Further, Jerome says that "they are anathema who say God has laid impossibilities upon man." Now what a man cannot fulfil by himself is impossible to him. Therefore a man can fulfil all the commandments of himself. Objection 3. Further, of all the commandments of the Law, the greatest is this, "Thou shalt love the Lord thy God with thy whole heart" (Mt. 27:37). Now man with his natural endowments can fulfil this command by loving God above all things, as stated above (3). Therefore man can fulfil all the commandments of the Law without grace. On the contrary, Augustine says (De Haeres. lxxxviii) that it is part of the Pelagian heresy that "they believe that without grace man can fulfil all the Divine commandments." I answer that, There are two ways of fulfilling the commandments of the Law. The first regards the substance of the works, as when a man does works of justice, fortitude, and of other virtues. And in this way man in the state of perfect nature could fulfil all the commandments of the Law; otherwise he would have been unable to sin in that state, since to sin is nothing else than to transgress the Divine commandments. But in the state of corrupted nature man cannot fulfil all the Divine commandments without healing grace. Secondly, the commandments of the law can be fulfilled, not merely as regards the substance of the act, but also as regards the mode of acting, i.e. their being done out of charity. And in this way, neither in the state of perfect nature, nor in the state of corrupt nature can man fulfil the commandments of the law without grace. Hence, Augustine (De Corrupt. et Grat. ii) having stated that "without grace men can do no good whatever," adds: "Not only do they know by its light what to do, but by its help they do lovingly what they know." Beyond this, in both states they need the help of God's motion in order to fulfil the commandments, as stated above (2,3). Reply to Objection 1. As Augustine says (De Spir. et Lit. xxvii), "do not be disturbed at his saying that they do by nature those things that are of the Law; for the Spirit of grace works this, in order to restore in us the image of God, after which we were naturally made." Reply to Objection 2. What we can do with the Divine assistance is not altogether impossible to us; according to the Philosopher (Ethic. iii, 3): "What we can do through our friends, we can do, in some sense, by ourselves." Hence Jerome concedes that "our will is in such a way free that we must confess we still require God's help."