When news of the bigamy of Hesse spread abroad, the doctor [Martin Luther] said with a serene countenance, “He’s a remarkable man. He has his [propitious] star. I think he wishes to obtain it [consent for his bigamy] through the emperor and the pope in order to gratify his desire. It’s also possible that he may defect from us as a result of this business.”
The editor remarks
Landgrave Philip of Hesse, a prominent evangelical prince who had been unhappily married to the daughter of Duke George of Saxony (cf. No. 275, n. 118) and had been resorting to a succession of prostitutes, finally decided to end his immoral conduct by marrying Margaret von der Sale. The theologian Martin Bucer (cf. No. 184, n. 64) interceded in his behalf with Luther and Melanchthon, who reluctantly gave their approval to the proposed marriage on condition that the arrangements be kept secret. On March 4, 1540, the marriage took place. When it became widely known soon after, a scandal resulted.
That because Philip was still legally married when he married his second wife. Luther wasn’t too bothered by it. I suppose the support of the Prince was more valuable to Luther than propriety.