Deuteronomy 17:17
15 you must select without fail a king whom the Lord your God chooses. From among your fellow citizens you must appoint a king—you may not designate a foreigner who is not one of your fellow Israelites. 16 Moreover, he must not accumulate horses for himself or allow the people to return to Egypt to do so, for the Lord has said you must never again return that way. 17 Furthermore, he must not marry many wives lest his affections turn aside, and he must not accumulate much silver and gold. 18 When he sits on his royal throne he must make a copy of this law on a scroll given to him by the Levitical priests. 19 It must be with him constantly, and he must read it as long as he lives, so that he may learn to revere the Lord his God and observe all the words of this law and these statutes and carry them out.
1 Kings 11:3
1 King Solomon fell in love with many foreign women (besides Pharaoh’s daughter), including Moabites, Ammonites, Edomites, Sidonians, and Hittites. 2 They came from nations about which the Lord had warned the Israelites, “You must not establish friendly relations with them! If you do, they will surely shift your allegiance to their gods.” But Solomon was irresistibly attracted to them. 3 He had 700 royal wives and 300 concubines; his wives had a powerful influence over him. 4 When Solomon became old, his wives shifted his allegiance to other gods; he was not wholeheartedly devoted to the Lord his God, as his father David had been. 5 Solomon worshiped the Sidonian goddess Astarte and the detestable Ammonite god Milcom.
Notes and References
"... Deuteronomy focuses much less on what the king must do than on what he must not do (17:16-17) ... These three restrictions “quite explicitly cut against the accepted pattern of kingship throughout the ancient Near East.” As Bible scholar Christopher Wright explains, “military power (the point of having great numbers of horses), the prestige of a large harem (frequently related to international marriage alliances), and great wealth (large amounts of silver and gold)—these were the defining marks of kings worthy of the title... But Deuteronomy starkly declares: ‘Not so in Israel.’” Why are weapons, wives, and wealth considered so dangerous? Cavalry and chariots signal a king’s self-glorification. When David’s sons Absalom and Adonijah seek to become king, each “provides himself with a chariot, horses, and fifty outrunners” (2 Samuel 15:1; 1 Kings 1:5) ... The desire to keep up a large army will also tempt the king to take advantage of his subjects. As Samuel warns, the king “will take your sons and appoint them as charioteers and horsemen, and they will serve as outrunners for his chariots” (1 Samuel 8:11). Vast numbers of wives, Deuteronomy worries, will undermine the king’s loyalty to God. The reader of Tanakh thinks immediately of King Solomon, the wisest of men who nevertheless lost his way: “He had seven hundred royal wives and three hundred concubines; and his wives turned his heart away” (1 Kings 11:3). Or, of Ahab, who married a Phoenician wife and soon began to worship Baal and Asherah (1 Kings 16:31-33) ..."
Held, Shai Give the People (Only Some of) What They Want: Deuteronomy and the King (pp. 1-10) Center for Jewish Leadership and Ideas, 2014