So they spread Absalom a tent upon the top of the house; and Absalom went in unto his father's concubines in the sight of all Israel.
Read Chapter 16
George Leo Haydock
Israel, who saw him enter the tents, (Calmet) on the flat roof, chap. xi. 2., and xii. 11. (Haydock)
The wives of the conquered king were reserved for the victor. Smerdis married all the wives of his predecessor, Cambyses. (Herodotus iii. 68, 83.) (Calmet)
He was expelled from his kingdom and fled as an exile to escape murder. You do not know of a son more wicked and bloodthirsty. Because he could not kill his father in his attempt to murder him, he defiled him with incest. By heaping crime on crime, he achieved an incest beyond all incest. He committed in public a thing most shameful to his father, a crime which is abominable in secret. Not only his absent father was made to look hideous by his son’s deadly crime, but the eyes of all were polluted by his public incest. - "The Governance of God 2.5"