(1.) King of the Ammonites in the time of Saul. The inhabitants of Jabesh-Gilead having been exposed to great danger from Nahash, sent messengers to Gibeah to inform Saul of their extremity. He promptly responded to the call, and gathering together an army he marched against Nahash. "And it came to pass that they which remained were scattered, so that two of them [the Ammonites] were not left together" (1 Samuel 11:1-11).
(2.) Another king of the Ammonites of the same name is mentioned, who showed kindness to David during his wanderings (2 Samuel 10:2). On his death David sent an embassy of sympathy to Hanun, his son and successor, at Rabbah Ammon, his capital. The grievous insult which was put upon these ambassadors led to a war against the Ammonites, who, with their allies the Syrians, were completely routed in a battle fought at "the entering in of the gate," probably of Medeba (2 Samuel 10:6-14). Again Hadarezer rallied the Syrian host, which was totally destroyed by the Israelite army under Joab in a decisive battle fought at Helam (2 Samuel 10:17), near to Hamath (1 Chronicles 18:3). "So the Syrians feared to help the children of Ammon any more" (2 Samuel 10:19).
(3.) The father of Amasa, who was commander-in-chief of Abasolom's army (2 Samuel 17:25). Jesse's wife had apparently been first married to this man, to whom she bore Abigail and Zeruiah, who were thus David's sisters, but only on the mother's side (1 Chronicles 2:16).