"Be fruitful and multiply" is a verse with a storied history. Whether in theology or natural law, this much-debated verse's explosive potential had gone largely dormant prior to the Reformation. For Luther, however, in the context of the debate surrounding monastic vows, this verse would once again take on new life. Fueled by the contributions of his fellow reformers - especially with regard to the normative nature of man's sexuality - a powerful new understanding of this verse emerged. This new understanding, a synthesis of Luther's own scriptural understanding coupled with powerful natural-philosophical insight from Melanchthon, would go on to play a significant role as former celibates abandoned their vows. It would also offer normative shape to the contours of Reformation marriage even as it took its place in such important works as the Augsburg Confession and Melanchthon's Apology.