Adam Clarke on 2 Samuel 10:2

I will show kindness unto Hanun the son of Nahash - We do not know exactly the nature or extent of the obligation which David was under to the king of the Ammonites; but it is likely that the Nahash here mentioned was the same who had attacked Jabesh-gilead, and whom Saul defeated: as David had taken refuge with the Moabites, (1Sam 22:3), and this was contiguous to the king of the Ammonites, his hatred to Saul might induce him to show particular kindness to David.