I gave thee thy master's house All that pertained to him as a king, which came, of course, to David, as his successor. Thy master's wives into thy bosom For the wives of a king went along with his lands and goods unto his successor, it being unlawful for the widow of a king to be wife to any but a king, as appears by the story of Adonijah. The expression in the text, however, does not necessarily signify that David married any of them; nor have we any proof that he did. Indeed, it is doubtful whether he could consistently with the law of God. See Leviticus 18:8; Leviticus 18:15. The meaning seems only to be, that God put them into David's power, together with Saul's house and other property. And gave thee the house of Israel Dominion over the twelve tribes. And if that had been too little, &c. He needed but have asked, and God would have given him all he could have reasonably desired.
Related Commentaries of 2 Samuel 12:8
2 Samuel 12:8
8 And I gave thee thy master's house, and thy master's wives into thy bosom, and gave thee the house of Israel and of Judah; and if that had been too little, I would moreover have given unto thee such and such things.