Sahih Bukhari Volume 007, Book 071, Hadith Number 591.
Narrated By Khalid bin Sad: 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 saying, 'This black cumin is healing for all diseases except As-Sam. 'Aisha said, 'What is As-Sam?' He said, 'Death."