2 Samuel 17:14, 23

And Absalom and all the men of Israel said, “The counsel of Hushai the Archite is better than the counsel of Ahithophel.” For the LORD had ordained to defeat the good counsel of Ahithophel, so that the LORD might bring harm upon Absalom.

When Ahithophel saw that his counsel was not followed, he saddled his donkey and went off home to his own city. He set his house in order and hanged himself, and he died and was buried in the tomb of his father.