It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he (peace and blessings be upon him) said: "'Al-hamdu lillah' (All praise is for Allah) is Umm al-Qur'an, the Seven Oft-Repeated (verses) and the Great Qur'an."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3955