Book of Mormon
27 Wherefore, my brethren, hear me, and hearken to the word of the Lord: For there shall not any man among you have save it be one wife; and concubines he shall have none;

28For I, the Lord God, delight in the chastity of women. And whoredoms are an abomination before me; thus saith the Lord of Hosts.
29Wherefore, this people shall keep my commandments, saith the Lord of Hosts, or cursed be the land for their sakes.

Book of Mormon, Book of Jacob Chapter 2:27-29