(9) باب فَضْلِ فَاتِحَةِ الْكِتَابِ
Narrated Abu Sa`id Al-Mu'alla:
While I was praying, the Prophet (ﷺ) 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."
Reference: Sahih al-Bukhari 5006
In-book reference: Book 66, Hadith 28
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 6, Book 61, Hadith 528