Holy Scripture teaches very distinctly that a sinner is not justified by good works, Rom. 3, 23-28; 4, 4. 5; Gal. 2, 21; 3, 10; etc. Good works are therefore "not necessary for salvation." But neither are good works "necessary to preserve faith," since the believer is preserved in faith unto salvation by the power of God, Phil. 1, 6; 1 Pet. 1, 5. Hence all who do good works in order to earn salvation by them are under the curse; for they are fallen from grace, Gal. 3, 10. 11; 5, 4. Holy Scripture, moreover, affirms that good works flow from faith alone or from the triumphant assurance of the believer that God already has bestowed heaven on him as a free gift of grace for Christ's sake, so that they are done freely, cheerfully, and willingly, without any coercion whatsoever, and without any thought of meriting even the least grace by them, Gal. 2, 20. In view of these facts it would seem to be out of place to speak of any reward of Christian good works.
Nevertheless Scripture itself in many places most emphatically assures the believers that their good works shall be liberally rewarded. "Great is your reward in heaven," Matt. 5, 12 ; Luke 6, 23. 35; "Every man shall receive his own reward according to his own labor," 1 Cor. 3, 8; "God is not unrighteous to forget your work and labor of love," Reb. 6, 10. In these and many other passages Holy Scripture speaks distinctly of a reward that shall be bestowed upon believers on account of their good works. This reward is granted both in this life, 1 Tim. 4, 8, and in the life to come, Luke 14, 14.
How are we to understand these statements of Scripture? Do they annul the doctrine of justification by grace through faith (sola fide)? In order to avoid any error of man's conceited reason on this point, we must remember two facts: In the first place, though Scripture speaks of a reward of Christian good works, it nevertheless teaches that this reward is of grace (Gnadenlohn) and not of merit, Rom. 4, 4. Luther, in his exegesis of Gal. 3, 22, explains this matter correctly when he says that, since the world does not reward believers for their good works, but rather hates them on account of them, Acts 5, 40; Rom. 8, 36; 1 Cor. 4, 13, God is so kind as to attach to them special promises of gracious rewards. Cf. St. L., IX, 443. So also the Apology says Art. V (III), 244 : "In the preaching of rewards, grace is set forth" ("In praedicatione praemiorum gratia ostenditu1").
So, then, we maintain on the basis of Scripture the two doctrines: a) The believer in Christ shall receive for his good works an abundant reward of grace (praemium gratiae), ὁ μισθὸς ὑμῶν πολύς, Matt. 5, 12; but b) all who demand a reward on account of their good works shall not only forfeit God's reward of grace, but also lose their salvation, Gal. 5, 4.
These two doctrines are clearly set forth also in Matt. 19, 27-30; 20, 1-16, where Christ, on the one hand, promises to His believing apostles a sure reward of grace and, on the other, declares that, whenever the demand of a reward is made on the basis of merit, "the first shall be last," Matt. 20, 16, that is, the first, or the self-righteous, shall be entirely rejected.
In the second place, God's free promises of reward made to His saints serve the excellent purpose of prompting the individual believer zealously to perform good works, Matt. 5, 12; Luke 6, 23. 35. To this truth the Apology points when it says Art. V (III), 79: "By these praises of good works (Matt. 5, 10) believers are undoubtedly moved to do good works" ('His praeconiis bonorum operum moventur haud dubie fideles ad bene operandum) ."
Luther stresses this point when he remarks that in all passages of Scripture which speak of the reward of the believer (Gen. 15, 1: "Thy exceeding great Reward"; Rom. 2, 6. 7, etc.) the godly are incited, comforted, and encouraged to continue, remain and conquer in doing what is good and in enduring what is evil, so that they may not become weary and dispirited." St. L., XVIII, 1810 ff.
The gracioua promises of reward which Scripture offers to believers therefore deny the doctrine of salvation by works or merit and confirm that of salvation by grace. This truth the Christian believer muat always bear in mind, especially since both the papists and modern rationalistic Protestants misuse the Scriptural doctrine of God's gracious reward of Christian good works in the interest of work-righteousness.
Luther states the matter very clearly when he writes St. L., VII, 677 ff. : "Then learn to reply correctly to those passages in which merit and reward are spoken of saying : I indeed hear that Christ says: 'Blessed are the poor in spirit; for theirs is the kingdom of heaven,' and: 'Blessed are ye when men persecute you for My sake, for great is your reward in heaven,' etc. But by these words He does not teach me the foundation upon which I should rest my salvation; but He by these words gives me a promise, showing me what comfort I should have in my suffering and Christian life. These two things you must not mingle into each other nor brew together; nor must you make a merit of that which God gives me freely in Christ through Baptism and the Gospel. For He does not say here that I could earn such things or that I no longer need Christ or Baptism, but rather that those are Christ's true disciples to whom He here preaches and who for His sake must suffer many things, so that they do not know how they may comfort themselves. Since people do not suffer them on earth, they should therefore in heaven all the more possess all things." (Cp. also Dr. Pieper's excellent presentation of the doctrine, Christl. Dogmatic, III, 64 ff.)