1 Kings 11:3-8

He had 700 wives of royal birth and 300 concubines. And in fact, they did turn his heart away from the LORD. In Solomon’s old age, they turned his heart to worship other gods instead of being completely faithful to the LORD his God, as his father, David, had been. Solomon worshiped Ashtoreth, the goddess of the Sidonians, and Molech, the detestable god of the Ammonites. In this way, Solomon did what was evil in the LORD’s sight; he refused to follow the LORD completely, as his father, David, had done. On the Mount of Olives, east of Jerusalem, he even built a pagan shrine for Chemosh, the detestable god of Moab, and another for Molech, the detestable god of the Ammonites. Solomon built such shrines for all his foreign wives to use for burning incense and sacrificing to their gods.