Luther on justification

The third incomparable grace of faith is this, that it unites the soul to Christ, as the wife to the husband; by which mystery, as the Apostle teaches, Christ and the soul are made one flesh. Now if they are one flesh, and if a true marriage - nay, by far the most perfect of all marriages - is accomplished between them (for human marriages are but feeble types of this one great marriage), then it follows that all they have becomes theirs in common, as well good things as evil things; so that whatsoever Christ possesses, that the believing soul may take to itself and boast of as its own, and whatever belongs to the soul, that Christ claims as his.

If we compare these possessions, we shall see how inestimable is the gain. Christ is full of grace, life, and salvation; the soul is full of sin, death, and condemnation. Let faith step in, and then sin, death, and hell will belong to Christ, and grace, life, and salvation to the soul. For, if he is a husband, he must needs take to himself that which is his wife’s, and, at the same time, impart to his wife that which is his. For, in giving her his own body and himself, how can he but give her all that is his? And, in taking to himself the body of his wife, how can he but take to himself all that is hers?

In this is displayed the delightful sight, not only of communion, but of a prosperous warfare, of victory, salvation, and redemption. For since Christ is God and man, and is such a person as neither has sinned, nor dies, nor is condemned - nay, cannot sin, die, or be condemned - and since his righteousness, life, and salvation are invincible, eternal, and almighty; when, I say, such a person, by the wedding-ring of faith, takes a share in the sins, death, and hell of his wife, nay, makes them his own, and deals with them no otherwise than as if they were his, and as if he himself had sinned; and when he suffers, dies, and descends to hell, that he may overcome all things, since sin, death, and hell cannot swallow him up, they must needs be swallowed up by him in stupendous conflict. For his righteousness rises above the sins of all men; his life is more powerful than all death; his salvation is more unconquerable than all hell.

Thus the believing soul, by the pledge of its faith in Christ, becomes free from all sin, fearless of death, safe from hell, and endowed with the eternal righteousness, life, and salvation of its Husband Christ. Thus He presents to Himself a glorious bride, without spot or wrinkle, cleansing her with the washing of water by the word; that is, by faith in the word of life, righteousness, and salvation. Thus He betrothes her unto Himself "in faithfulness, in righteousness, and in judgment, and in loving kindness, and in mercies" (Hosea ii. 19, 20).

Who then can value highly enough these royal nuptials? Who can comprehend the riches of the glory of this grace?

Martin Luther, On the Freedom of a Christian Man