2 Samuel 15:7-10

7Now it came to pass after forty years that Absalom said to the king, “Please, let me go to Hebron and pay the vow which I made to the Lord.

8For your servant took a vow while I dwelt at Geshur in Syria, saying, ‘If the Lord indeed brings me back to Jerusalem, then I will serve the Lord.’ ”

9And the king said to him, “Go in peace.” So he arose and went to Hebron.

10Then Absalom sent spies throughout all the tribes of Israel, saying, “As soon as you hear the sound of the trumpet, then you shall say, ‘Absalom reigns in Hebron!’ ”