It is narrated from Sa'id bin Jubair, may Allah have mercy on him, regarding the verse: ﴿وَلَقَدْآتَيْنَاكَسَبْعًامِنَالْمَثَانِيوَالْقُرْآنَالْعَظِيمَ﴾[الحجر: 87] He says: "By this is meant Umm al-Qur'an (Surah al-Fatiha)." Ibn Jurayj says, my father said: Sa'id bin Jubair recited the complete (Surah al-Fatiha) to me and then said: 'Bismillah-ir-Rahman-ir-Raheem is its seventh verse.' Sa'id says: Just as I have recited to you, so did Ibn Abbas, may Allah be pleased with them both, recite it and say: 'Bismillah-ir-Rahman-ir-Raheem is its seventh verse.' Ibn Abbas, may Allah be pleased with them both, said: (Allah) has kept this preserved for you with Him and has not given it to anyone before you."
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 210