Sahih Bukhari
Virtues of the Quran
Volume: 006 / Book Number: 061 / Hadith Number: 528
Narrated Abu Sa'id Al-Mu'alla:
While I was praying, the Prophet called me but I did not respond to his call. Later I said, "O Allah's Apostle! I was praying." He said, "Didn't Allah say: 'O you who believe! Give your response to Allah (by obeying Him) and to His Apostle when he calls you'?" (8.24)
He then said, "Shall I not teach you the most superior Surah in the Qur'an?" He said, '(It is),
'Praise be to Allah, the Lord of the worlds. ' (i.e., Surat Al-Fatiha) which consists of seven repeatedly recited Verses and the Magnificent Qur'an which was given to me."