bigamy
Genesis Chapter 4:19
And Lamech took unto him two wives: the name of the one was Adah, and the name of the other Zillah.
Deuteronomy Chapter 17:17
Neither shall he multiply wives to himself, that his heart turn not away: neither shall he greatly multiply to himself silver and gold.
1 Corinthians Chapter 7:2
Nevertheless, to avoid fornication, let every man have his own wife, and let every woman have her own husband.