2 Samuel 16:21

Thy father's concubines. See on 1 Kings 2:17. Ahithophel was aware of the fact that the success of Absalom’s rebellion was by no means certain. He knew that after the first burst of enthusiasm a reaction would come. David’s position was far from hopeless. He had with him able generals and an experienced army. Many of the people had not yet forgotten him. If the situation went against Absalom and David should succeed in getting back his kingdom, the king might be in a mood to forgive Absalom. But there would be no conciliatory spirit toward Absalom’s chief supporters. In such a case Ahithophel would be regarded as the most guilty and thus the most worthy of severe punishment. Such a situation this wily counselor was determined to prevent at all costs. His first concern, therefore, was to draw Absalom into a position that would make the breach with his father absolute and irreconcilable. His counsel was given with satanic cunning.

Be strong. Ahithophel contended that since the step being advised would prove to the people that Absalom was not going back on his rebellion, the men who were with him would give themselves completely to his cause.