Jamieson, Fausset & Brown

I gave thee thy master's house, and thy master's wives--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.