Good original question and many good answers. The Law said long before Israel ever had a king that he was not to have multiple wives. David and Solomon simply ignored that, and both of them paid a very high price for it. David's family was ripped apart because of all the jealousies that naturally result from polygamy, and Solomon's heart was not right with God because of all his wives. The fact that God loved them both in spite of their sin is just an example of His grace, and I am thankful that He loves me in spite of my sin. But at least I ain't got multiple wives to worry about.
Deuteronomy 17:14�20 (NKJV)
14�When you come to the land which the Lord your God is giving you, and possess it and dwell in it, and say, �I will set a king over me like all the nations that are around me,�
15you shall surely set a king over you whom the Lord your God chooses; one from among your brethren you shall set as king over you; you may not set a foreigner over you, who is not your brother.
16But he shall not multiply horses for himself, nor cause the people to return to Egypt to multiply horses, for the Lord has said to you, �You shall not return that way again.�
17Neither shall he multiply wives for himself, lest his heart turn away; nor shall he greatly multiply silver and gold for himself.
18�Also it shall be, when he sits on the throne of his kingdom, that he shall write for himself a copy of this law in a book, from the one before the priests, the Levites.
19And it shall be with him, and he shall read it all the days of his life, that he may learn to fear the Lord his God and be careful to observe all the words of this law and these statutes,
20that his heart may not be lifted above his brethren, that he may not turn aside from the commandment to the right hand or to the left, and that he may prolong his days in his kingdom, he and his children in the midst of Israel.
