2 Samuel 15:7-8

And it came to pass at the end of forty years, that Absalom said unto the king, I pray thee, let me go and pay my vow, which I have vowed unto Jehovah, in Hebron.

For thy servant vowed a vow while I abode at Geshur in Syria, saying, If Jehovah shall indeed bring me again to Jerusalem, then I will serve Jehovah.