"There is something else. You remember what Joab did to me by killing the two commanders of Israel's armies, Abner son of Ner and Amasa son of Jether. You remember how he murdered them in time of peace as revenge for deaths they had caused in time of war. He killed innocent men, and now I bear the responsibility for what he did, and I suffer the consequences. 1
References for 1 Kings 2:5
2.5 a 2 S 3.27; b 2 S 20.10.