Musnad Ahmad 30:3816

Hashim narrated to us, Shu'bah narrated to us, Qatadah said: He informed me, he said: I heard Hilal ibn Yazid—a man from Banu Mazin ibn Shayban—say: I heard Abu Hurayrah saying about the Prophet, peace and blessings of Allah be upon him: "Indeed, this black seed—meaning nigella—is a cure for everything except the *sam*." Qatadah said: And the *sam* is death.