Because he has done this thing and has shown no pity, he must pay for the lamb four times over.”
It seems to have been a great while after David had been guilty of adultery with Bath-sheba before he was brought to repentance for it. For, when Nathan was sent to him, the child was born (Sa2 12:14), so that it was about nine months that David lay under the guilt of that sin, and, for aught that appears, unrepented of.
Commenting on 2 Samuel 12:1-14
And Nathan said to David, thou art the man,.... The rich man, or who is designed by him in the parable, and answers to him (t): thus saith the Lord God of Israel, I anointed thee king over Israel; that is, ordered Samuel to anoint him, who did, Sa1 16:1; to which this chiefly refers; and after that he was anointed first by the tribe...
2Sa 12:5-6 David was so enraged at this act of violence on the part of the rich man, that in the heat of his anger he pronounced this sentence at once: “As the Lord liveth, the man who did this deserves to die; and the lamb he shall restore fourfold.” The fourfold restoration corresponds to the law in Exo 22:1.
Commenting on 2 Samuel 12:5-6