Sayyiduna Abdullah bin Umayr al-Ashja'i (may Allah be pleased with him) narrates: I heard the Prophet (peace and blessings be upon him) say: "When someone rebels against you while you are united behind a ruler, and that person wants to split the staff of the Muslims and scatter their unity, then kill that person."
Al-Tabarani recorded it. Its chain contains narrators whom I do not know.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب قتال أهل البغي / 10433