2 Samuel 15:10-12

But while he was there, he sent secret messengers to all the tribes of Israel to stir up a rebellion against the king. “As soon as you hear the ram’s horn,” his message read, “you are to say, ‘Absalom has been crowned king in Hebron.’” He took 200 men from Jerusalem with him as guests, but they knew nothing of his intentions. While Absalom was offering the sacrifices, he sent for Ahithophel, one of David’s counselors who lived in Giloh. Soon many others also joined Absalom, and the conspiracy gained momentum.