The Messenger of Allah ﷺ said to Ammar, "The transgressing party will kill you."
حدثنا محمد بن جعفر حدثنا شعبة عن خالد عن عكرمة
أن رسول الله ﷺ قال لعمار تقتلك الفئة الباغية
Its isnad is sahih. Khalid is Ibn Mihran al-Hadhdha, a well-known trustworthy narrator, and Ikrima is the freedman of Ibn Abbas, also a well-known trustworthy narrator. The hadith has already appeared at 10933.