Rehob is primarily known as the father of Hadadezer, king of Zobah (an Aramean kingdom in Syria). He is mentioned in connection with David's wars against the Arameans. The name Rehob also appears as a place name and belongs to several people in the Old Testament, but the most prominent one is the father of Hadadezer.
David defeated Hadadezer, the son of Rehob, when Hadadezer went to restore his dominion at the Euphrates River. David took many prisoners and great spoils of war.
4David captured from him seventeen hundred horsemen and twenty thousand foot soldiers. He hamstrung all the chariot horses, but he left enough for a hundred chariots.
6Then David stationed garrisons in Aram of Damascus, and the Arameans became his servants and brought him tribute. The LORD gave David victory wherever he went.
The same account of David's victory over Hadadezer, king of Zobah, is retold in 1 Chronicles, although Rehob's name is not always explicitly mentioned there.
4David captured from him a thousand chariots, seven thousand horsemen, and twenty thousand foot soldiers. He hamstrung all the chariot horses, but kept a hundred chariots for himself.