From Sahih Bukhari (Hadith 5687):
Narrated Khalid bin Sa`d:We went out and Ghalib bin Abjar was accompanying us. He fell ill on the way and when we arrived at Medina he was still sick. Ibn Abi 'Atiq came to visit him and said to us, "Treat him with black cumin. Take five or seven seeds and crush them (mix the powder with oil) and drop the resulting mixture into both nostrils, for `Aisha has narrated to me that she heard the Prophet (ﷺ) saying, 'This black cumin is healing for all diseases except As-Sam.' Aisha said, 'What is As-Sam?' He said, 'Death
Reference: Bukhari 5687