Musnad Ahmad Hadith 8061

It is narrated from Abu Hurairah (may Allah be pleased with him) that he heard the Noble Prophet (ﷺ) say: Whoever withdraws from obedience to the leader and separates from the community and dies in that state, his death is a death of ignorance (Jahiliyyah). And whoever rises against my Ummah, striking the righteous and the wicked alike, showing no regard for the believer, and does not fulfill his covenant with those with whom he has made a pact, then he is not of my Ummah. And whoever fights under a banner out of blind following (nationalistic or linguistic), becomes angry for that cause, fights for that cause, and supports that cause, and is killed, then his death is like the death of ignorance (Jahiliyyah).