Musnad Ahmad 30:2662

Isma'il ibn 'Umar narrated to us, he said: Ibn Abi Dhi'b narrated to us, from al-Maqburi, from Abu Hurayrah, from the Messenger of Allah, peace and blessings of Allah be upon him, who said: "Praise be to Allah (Al-Hamdu lillahi) is the Mother of the Qur'an, the Mother of the Book, and the Seven Oft-Repeated Verses."