Dr. Luther continues his discussion of the true knowledge and worship of God, in Christ Jesus, by grace through faith in His righteousness, in contrast to the idolatry of works righteousness. From his Lectures on Galatians (CPH 1963), re: Gal. 4:8-9:
"There is no middle ground between human working and the knowledge of Christ; if this knowledge is obscured, it does not matter whether you become a monk or a heathen afterwards.
"Therefore it is completely insane when the papists and the Turks do battle against each other about religion and the worship of God; each contends that he has the true religion and worship of God. In fact, even the monks are not in agreement among themselves; one wants to be regarded as holier than another merely because of some foolish outward ceremonies, when in their hearts the opinions of them all are more alike than eggs. For this is what they all think: ‘If I do this work, God will have mercy on me; if I do not, He will be wrathful.’
"Therefore every man who falls away from the knowledge of Christ necessarily rushes into idolatry; for he must invent a form for God that does not exist anywhere, as the Carthusian trusts that because of his observance of his monastic rule, and the Turk that because of his observance of the Koran, he pleases God and will receive from Him the reward for his labor.
"A God of this kind, who forgives sins and justifies in this manner, cannot be found anywhere. Therefore it is all a vain imagination and a dream, the invention of an idol in the heart. For nowhere has God promised that He intends to justify men and save them on account of religious orders, observances, and forms of worship that have been thought up and established by men. In fact, as all Scripture attests, nothing is more abominable to God than such self-chosen works and forms of worship; He even overthrows kingdoms and empires on account of such things.
"Therefore all those who trust in their own ability and righteousness are serving a god who by nature is no god but is a god only in their opinion. For He who is true God by nature speaks this way: ‘I am not pleased with any righteousness, wisdom, or religious observance except the one by which the Father is glorified through the Son. Whoever takes hold of this Son and of Me or of My promise in Him through faith—to him I am God, to him I am Father; him I accept, justify, and save. All the rest remain under wrath, because they worship him who by nature is no god.’
"Whoever defects from this doctrine will necessarily fall into an ignorance of God and an ignorance of the righteousness, wisdom, and proper worship of God. He will be an idolater, remaining under the Law, sin, death, and the rule of the devil; and everything that he does will be lost and condemned."