Absalom sent for Ahithophel the Gilonite, David’s counselor, from his city, even from Giloh, while he was offering the sacrifices. The conspiracy was strong, for the people increased continually with Absalom. Bible

“sent for Ahithophel.” Ahithophel had been David’s counselor, but apparently he had become angry and bitter against David after David had sex with his granddaughter Bathsheba and arranged for her husband Uriah to be killed. Ahithophel was the father of Eliam (2 Sam. 23:34), and Eliam was the father of Bathsheba (2 Sam. 11:3), making Ahithophel the grandfather of Bathsheba. Absalom would have noticed that the relationship between Ahithophel and David had cooled, and likely had spoken with Ahithophel while they were both at the palace, and that is why he was confident enough to send for Ahithophel even though in the past Ahithophel had been very close to David. Now that David had a rival, Ahithophel sided with him. His anger and bitterness was his undoing, because when Absalom rejected his advice and took instead the advice of Hushai the Arkite (2 Sam. 17:1-14) he felt so rejected and dishonored that he took his own life (2 Sam. 17:23). [For more on Ahithopehl see commentary on 2 Samuel 16:21 and 2 Samuel 17:1].

Commentary for: 2 Samuel 15:12