To Leonhard Beyer, pastor at Zwickau.
God's grace and peace through our Lord Jesus Christ. Worthy, dear pastor, special good friend!
We have received your letter, in which you indicate that one has slept with his deceased wife's sister and desires to marry her, if it may be done with God and if it is permitted to them. Thereupon we add you to know: That we hold and conclude together that in this case the marriage is not to be permitted at all. For first of all, it is true, as you know, that it is God's commandment that one should not marry together in the nearer ranks; and that God would punish such unnatural intermarriage in all the world is clearly shown by the text Deut. 18.
Now this case is in primo gradu affinitatis (in the first degree of affinity). For if husband and wife are one flesh, the wife's sister is held equal to the husband's sister; for which reason also imperial rights forbid this case, Codice de incestuosis et inutilibus nuptiis (in the code of incestuous and useless marriages). We also consider, if these persons come together, that they would have unpeaceful consciences all their lives, because of the case itself, and because of the aversion; and will undoubtedly come much better to a peaceful conscience, if they do away from each other.
Thus, one must not allegory Jacob's example here. For God Himself afterwards in Moses forbade such a marriage, and it is also not clearly expressed in Moses that one
the deceased wife's sister may free. Also one has no example. And although remedies for this are sought from Moses, such marriages are nevertheless forbidden by nature and by the authorities.
Therefore they are contrary to the saying Matth. 19, 6: Quos Deus conjunxit. About all this, you know that such examples are very annoying, and nefarious people take cause from them for incest. As it has been found, unfortunately, in some cases, that such people have wanted to excuse themselves with the previous annoying example. From these reasons we conclude that in the reported case no marriage is to be permitted, and if the people are not satisfied with our concern, you may send them to court. But if the people are in great pain because of sin and disgrace, and also danger from friendship, let them be comforted with the gospel, and especially let them know that they will have unpeaceful consciences in marriage, for the reasons reported above; and they will be more easily comforted if they separate from each other; so also the authorities are obliged to make peace between the friendship.
We do not want to take your kind opinion on your writing, because we are completely inclined to show you good will. Date Wittenberg, Monday after Antonii, Anno 1535.
Justus Jonas, Provost.
Martinus Luther, both doctors. Philippus Melanchthon.