Bible Permits Polygamy...Contradicts Itself
Deu 17:14-20 When you have come into the land that the Lord your God is giving you, and have taken possession of it and settled in it, and you say, "I will set a king over me, like all the nations that are around me," (15) you may indeed set over you a king whom the Lord your God will choose. One of your own community you may set as king over you; you are not permitted to put a foreigner over you, who is not of your own community. (16) Even so, he must not acquire many horses for himself, or return the people to Egypt in order to acquire more horses, since the Lord has said to you, "You must never return that way again." (17) And he must not acquire many wives for himself, or else his heart will turn away; also silver and gold he must not acquire in great quantity for himself. (18) When he has taken the throne of his kingdom, he shall have a copy of this law written for him in the presence of the levitical priests. (19) It shall remain with him and he shall read in it all the days of his life, so that he may learn to fear the Lord his God, diligently observing all the words of this law and these statutes, (20) neither exalting himself above other members of the community nor turning aside from the commandment, either to the right or to the left, so that he and his descendants may reign long over his kingdom in Israel. (NRSV)
Above is the law which concerned kings of Israel. Verse 17 says a king of Israel "must not acquire many wives for himself, or else his heart will turn away."
2Sa 5:13 In Jerusalem, after he came from Hebron, David took more concubines and wives; and more sons and daughters were born to David.
David violated Deu 17:17 when he acquired many wives.
1Ki 15:4-5 Nevertheless for David's sake the Lord his God gave him a lamp in Jerusalem, setting up his son after him, and establishing Jerusalem; (5) because David did what was right in the sight of the Lord, and did not turn aside from anything that he commanded him all the days of his life, except in the matter of Uriah the Hittite.
1Ki 15:5 contradicts Deu 17:17 and 2Sa 5:13, as David turned aside from the commandment in Deu 17:17; the commandment which, according to Deu 17:18, was to be in the copy of the law that was to be written by a king of Israel once they had taken the throne; the commandment that was supposed to "remain with" David and be read in "all the days of his life, so that he may learn to fear the Lord his God..."
Not only is the Bible contradictory concerning polygamy, it also permits it. 1Ki 15:5 says "David did what was right in the sight of the Lord...all the days of his life," therefore when he acquired many wives in the sight of the Lord, he did what was "right."