I confess that I cannot forbid a person to marry several wives, for it does not contradict the Scripture. If a man wishes to marry more than one wife he should be asked whether he is satisfied in his conscience that he may do so in accordance with the Word of God. In such a case the civil authority has nothing to do in the matter.
Letter to Chancellor Gregory Bruck, January 13, 1524
(De Wette II, 459, pp. 329, 330)