Jamieson, Fausset and Brown on Genesis 20:9

9. Then Abimelech called Abraham, and said ... What hast thou done?--In what a humiliating plight does the patriarch now appear--he, a servant of the true God, rebuked by a heathen prince. Who would not rather be in the place of Abimelech than of the honored but sadly offending patriarch! What a dignified attitude is that of the king--calmly and justly reproving the sin of the patriarch, but respecting his person and heaping coals of fire on his head by the liberal presents made to him.