Musnad Ahmad 30:3203

Isma'il narrated to us, from Ayyub, from Ghaylan ibn Jarir, from Ziyad ibn Riyach, from Abu Hurayrah, who said: "Whoever exits from obedience and separates from the community, then dies, his death is a death of Jahiliyyah (pre-Islamic ignorance). And whoever goes out against my nation, striking its righteous and its wicked, not sparing its believer, and not fulfilling the covenant of those who have a covenant with it, then he is not of my nation. And whoever is killed under a blind banner, calling to partisanship, or becoming angry for partisanship, or fighting for partisanship, then his killing is a killing of Jahiliyyah."