And thy master’s wives ... - According to Eastern custom, the royal harem was a part of the royal inheritance. The prophets spoke in such matters according to the received opinions of their day, and not always according to the abstract rule of right. (Compare Matthew 19:4-9.)
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.