Musnad Ahmad 30:2065

Mu'awiyah narrated to us, Abu Ishaq narrated to us, from Suhayl ibn Abi Salih, from his father, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Allah has guaranteed for the one who goes out in His cause—nothing drives him out except belief in Me and affirmation of My messengers—that I shall admit him into Paradise, or return him to his dwelling from which he went out, having attained what he attained of reward or spoils."