John Calvin on Genesis 4:19

19. And Lamech took unto him two wives . We have here the origin of polygamy in a perverse and degenerate race; and the first author of it, a cruel man, destitute of all humanity. Whether he had been impelled by an immoderate desire of augmenting his own family, as proud and ambitious men are wont to be, or by mere lust, it is of little consequence to determine; because, in either way he violated the sacred law of marriage, which had been delivered by God. For God had determined, that “the two should be one flesh,” and that is the perpetual order of nature. Lamech, with brutal contempt of God, corrupts nature’s laws. The Lord, therefore, willed that the corruption of lawful marriage should proceed from the house of Cain, and from the person of Lamech, in order that polygamists might be ashamed of the example.