2 Samuel 17:14, 23

Absalom and all the men of Israel said, “The advice of Hushai the Arkite is better than that of Ahithophel.” For the LORD had determined to frustrate the good advice of Ahithophel in order to bring disaster on Absalom.

When Ahithophel saw that his advice had not been followed, he saddled his donkey and set out for his house in his hometown. He put his house in order and then hanged himself. So he died and was buried in his father’s tomb.