Did God Disapprove of David's Polygamy?
According to John MacArthur, "...David committed adultery with a whole bunch of women...," referring supposedly to his numerous wives and concubines.

Of course, few would argue that God strongly disapproved of his adulterous relationship with Bathsheba. However, there is no hint whatsoever in Scripture that God ever disapproved of David having numerous wives and concubines.Second Samuel 12:7-8 is often used by pro-polygamists to say that God not only approved of David having numerous wives, but he actually gave David those wives, including the wives of Saul.

Thus says the LORD God of Israel: "I anointed you king over Israel, and I
delivered you from the hand of Saul. I gave you your master's house and your master's wives into your keeping, and gave you the house of Israel and Judah. And if that had been too little, I also would have given you much more!"

Taken in context, Nathan the prophet was sent by God to confront David about his sins. David had committed adultery with Bathsheba. Then, to cover it up, he arranged to have her husband Uriah killed in battle. Within that context, God told David through Nathan that he had given David Saul's wives. However, opponents of polygamy have come up with numerous explanations to try and make this Scripture say something other than what it plainly says. The most common explanation goes something like this:

Sure, the Bible states that God gave David Saul's wives, but that is just a figure of speach. In ancient times, it was commonplace for a new king to take possession of everything owned by the former king, including his wives.

According to Jamieson, Fausset & Brown:

The phraseology means nothing more than that God in His providence had given David, as king of Israel, everything that was Saul's. The history furnishes conclusive evidence that he never actually married any of the wives of Saul. But the harem of the preceding king belongs, according to Oriental notions, as a part of the regalia to his successor.

So what opponents of polygamy tell us we're supposed to believe is that God didn't really give David Saul's wives because that would have been just plain wrong. We're supposed to believe that Nathan was simply using a figure of speach to say God gave David everything Saul had except for Saul's wives. Or perhaps God gave David Nathan's wives, but he didn't want them. Perhaps they were too ugly. Or perhaps God gave David Saul's wives, but he didn't really want David to take them because that would have been wrong. Perhaps God was just toying with David, playing the part of the serpent to see if David would eat the forbidden fruit.

Of course, this is all silly reasoning. James 1:13 plainly states:

Let no one say when he is tempted, "I am tempted by God"; for God cannot be tempted by evil, nor does He Himself tempt anyone (NKJV).

Therefore, if God disapproved of David's polygamy, there is no indication of that disapproval in Scripture. There is, however, a strong indication that God gave David Saul's wives. Whether or not David actually married Saul's wives seems beside the point.