M'lakhim Alef (1 Ki) 2:5

“Moreover, you are aware of what Yo’av the son of Tz’ruyah did to me, that is, what he did to the two commanders of the armies of Isra’el, Avner the son of Ner and ‘Amasa the son of Yeter — he killed them, shedding the blood of war in peacetime, putting the blood of war on the belt around his waist and the shoes on his feet.