The Messenger of Allah ﷺ said, "A disbeliever and the one who killed him will never be gathered together in the Fire."
أن رسول الله ﷺ قال: لا يجتمع كافر وقاتله في النار أبدا.
Muslim narrated it in the Book of Leadership (1891:130) via Ismail bin Jafar, from Ala, from his father, from Abu Hurairah, who said, and then he mentioned it.