John Calvin Commentary Genesis 4:19

"And Lamech took unto him two wives: the name of the one was Adah, and the name of the other Zillah." — Genesis 4:19 (ASV)

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, devoid of all humanity. Whether he had been driven by an immoderate desire of increasing his own family, as proud and ambitious men are accustomed to be, or by mere lust, it is of little importance to determine; because either way he violated the sacred law of marriage, which had been given 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, so that polygamists would be ashamed of the example.