But to put vanities aside, the word “return” has two uses in the Scriptures, one legal, the other evangelical. In its legal use it is an expression of exacting and imperious command, which requires not merely an endeavor but a change of the whole life. Jeremiah frequently makes this use of it, as when he says: “Return every one of you from his evil way” [Jer. 18:11; 25:5; 35:15] and “Return to the Lord” [Jer. 4:1]; for there it quite plainly involves obedience to the demands of all the precepts. In its evangelical use it is an expression of divine comfort and promise, by which nothing is demanded from us, but the grace of God is offered to us, as, for instance, in Psalm 15[14:7]: “When the Lord turns the captivity of Zion,” and Psalm 22: “Return, O my soul, to your rest.” Zechariah, therefore, has given us the briefest possible epitome of both kinds of preaching, both of law and of grace; for it is nothing but law, law at its peak, when he says, “Return to me,” and it is grace when he says, “I will return to you.” So to the extent that free choice is proved by the expression “Love the Lord!” or by any other particular expression of the law, to that extent it is proved by this summary expression of the law, “Return!” It is therefore the mark of a discerning reader of Scripture to notice what are words of law and what of grace, so as not to have them all jumbled up as the filthy Sophists and this yawning Diatribe do.
The Bondage of the Will
Luther’s Works Vol. 33