Martin Luther approved of polygamy

Luther and Melanchton - who were not opposed to polygamy on principle - granted Philip von Hesse a bigamous marriage in 1539, on condition that it would remain secret.

It almost happened. The Protestant Reformation nearly stayed true to principle. If Christ's bride was a universal catholic church, then monogamy must be correct. But if Christ's brides were the various denominations, perhaps even the various local churches (the New Testament model), then polygny was just and righteous.

Luther and Melanchton knew that this was a political hot potato, thus their request to keep it a secret. But they had no objection in principle. They were both right and wise. Unfortunately, modern followers are not nearly so righteous or wise.

Rampant Reformation & Enlightenment Polygamy for Christians

As soon as the Bible could be read in the vernacular, the polygamy of the patriarchs began to stimulate the imagination. It suffices to remind of the Anabaptist Jan van Leyden who openly propagated polygamy in Munster in 1534, of the 'Dialogus Nebuli' written in 1541 by Lening on instigation of Philip van Hesse, who wanted to obtain permission for a bigamous marriage from Luther and Melanchton. In 1563, the former Franciscan Bernardino Ochino, a Calvinist with growing sympathy for Anabaptism, wrote his 'XXX Dialogues'. Only in 1823 was discovered the manuscript 'De doctrina' written by Milton simultaneously with 'Paradise Lost'. In 1637 Johan Lyserus (Leyser) writes a 'Discursus de Polygamia', and in 1676 he publishes a book wherein is written that Adam had many ribs: 'Das Koenigliche Mark aller Laender'. 'Polygamia Triumphatrix' is published in 1682. Think also of the former Methodist Westley Hall and the 'Thelyphthora' published in 1780 by the equally apostate Martin Madan.

- Source: http://d-sites.net/english/eros01.htm