Q. Why did God give David all of Saul’s wives and break his own law that said Israel’s king “must not take many wives“?
I think this should be of concern to us, although not primarily for the reason that you give.
While the law you cite does appear, on the face of it, to prohibit Israel’s kings from marrying multiple wives, the intention of that law is to forbid marriage alliances with the surrounding pagan countries, as the justification for the law makes clear: “or his heart will be led astray.” It was understood that a women who went to a foreign country for a marriage alliance would still be allowed to worship her own gods, and if her husband really wanted to please his father-in-law (who might be a more powerful king), he might join in this worship.
This is precisely what happened to Solomon: “He had seven hundred wives of royal birth [i.e. through marriage alliances] and three hundred concubines, and his wives led him astray. As Solomon grew old, his wives turned his heart after other gods, and his heart was not fully devoted to the Lord his God, as the heart of David his father had been. He followed Ashtoreth the goddess of the Sidonians, and Molek the detestable god of the Ammonites.”
I think we can safely assume that if an Israelite king had married multiple wives who had all been faithful followers of the God of Israel, his heart would not have been “led astray,” and so the spirit, at least, of the commandment in Deuteronomy would not have been broken.
However, as I said, God giving Saul’s wives to David raises other concerns. It would appear that Saul had something of a royal harem (though certainly nowhere near as large as Solomon’s), and that David was allowed to make this harem his own when he became king. (This is the only place in the story of David where this is mentioned, so we have to infer the details.) Ordinarily the harem would never come to belong to the next king because sons succeeded their fathers on the throne and there was a prohibition in the law of Moses against a father and son marrying the same woman. But since David was starting a new dynasty, i.e. he was not the son of Saul, it was legal for him to make these women, who had become widows upon Saul’s death, his wives.
We may nevertheless still be concerned that David may have done this primarily to consolidate his hold on the kingship, rather than because he wanted to love and care for these women as his wives. We see this illustrated later in the biblical story, when there’s a rivalry between David’s own sons Solomon and Adonijah to succeed him on the throne. Adonijah wants to marry Abishag the Shunamite, a woman who had kept David warm in bed when he was old but who had not had sexual relations with him (so it was legal for Adonijah to marry her). But Solomon recognizes that Adonijah is trying to displace him, even though he’s David’s own choice for his successor, and consolidate a rival claim to the throne by doing the closest thing he can to taking over the royal harem. So Solomon replies to his messenger, “Why do you request Abishag the Shunammite for Adonijah? You might as well request the kingdom for him.”
However, we might observe that even if David’s primary motive was not to love and care for Saul’s widows, because he married them, they were cared for in a way that they probably would not have been otherwise. One of the realities of the story of redemption in the Old Testament is that it unfolds within a cultural context in which women are dependent on men for support, and many arrangements have to be understood in that light. We also see in the biblical story that well after David came to the throne, there was still sentiment in various parts of Israel to restore the house of Saul, and these women might actually have been in danger from partisans of David who wanted to quell that sentiment. Much of this is speculative, but I believe it helps explain why God might have allowed David to take over Saul’s harem.
There’s still one more important concern, though. It’s actually while the prophet Nathan is in the course of rebuking David for his sin against Bathsheba that he reminds David that God let him do this. Nathan’s message is that David had no grounds to want another man’s wife because he already had so many wives of his own: “I gave your master’s house to you, and your master’s wives into your arms. I gave you all Israel and Judah. And if all this had been too little, I would have given you even more. Why did you despise the word of the Lord by doing what is evil in his eyes? You struck down Uriah the Hittite with the sword and took his wife to be your own.”
As a consequence, Nathan says, David will suffer retributive justice: What he did to someone else will be done to him. However, it doesn’t seem that it’s really going to be done to David himself; instead, someone else will suffer for his wrongdoing: “Before your very eyes I will take your wives and give them to one who is close to you, and he will sleep with your wives in broad daylight. You did it in secret, but I will do this thing in broad daylight before all Israel.”
In other words, because David tried to get away secretly with sleeping with another man’s wife, someone else will sleep with his wives openly. It seems that it’s actually David’s wives who suffer this punishment, not David himself. The women ultimately affected were ten concubines whom David left behind to “take care of the palace” when he fled for his life from a rebellion launched by his son Absalom. Upon being advised that this would consolidate his claim on the throne, Absalom slept with these women; once he was defeated and killed and David returned, David put them in seclusion. They were provided for and protected, but “they lived as if they were widows,” no longer his wives.
The reader of the Bible is distressed to think that these innocent women suffered such a fate as some kind of divine judgment against somebody else. It is true that as the story of redemption continues to unfold over the course of the Bible, and particularly as the coming new covenant is announced by Jeremiah and Ezekiel, there’s a move away from judgments like these that affect an offender’s family towards individual punishments that target the individual responsibe. Jeremiah, for example, in his new covenant oracle, says that this proverb will no longer be quoted, “The parents have eaten sour grapes, and the children’s teeth are set on edge.”
Speaking through Ezekiel, God similarly objects to the people of Israel quoting this same proverb: “You ask, ‘Why does the son not share the guilt of his father?’ Since the son has done what is just and right and has been careful to keep all my decrees, he will surely live. The one who sins is the one who will die. The child will not share the guilt of the parent, nor will the parent share the guilt of the child. The righteousness of the righteous will be credited to them, and the wickedness of the wicked will be charged against them.”
So we may at least say that there is a development within redemptive history away from corporate or family punishments toward individual punishments, which seem to us to be much more in keeping with the just character of God. Nevertheless we still feel very badly for, and have continuing concerns about, those who lived in the time before this development, such as David’s ten concubines.
Perhaps the most we can say about their situations is to realize that our sins inevitably do affect those around us, and they affect most the people who are closest to us. Whether this is the result of direct divine judgment, or the result of the way God set up the moral universe, the harm we will do to those we love the most if we choose to sin is one more reason for us to turn away from that wrong choice and instead follow a course of action that will bring help and blessing to all those around us.