Sahih Bukhari

Narrated Yahya:I asked Aba Salama, ""Which Sura of the Qur'an was revealed first?"" He replied, ""O you, wrapped-up' (Al-Muddaththir)."" I said, ""I have been informed that it was, 'Read, in the Name of your Lord who created (i.e. Surat Al-Alaq)...similar to the narration related by `Ali bin Al-Mubarak, 444 above