Musnad Ahmad 30:1632

Sulayman ibn Dawud narrated to us, Shu'bah informed us, from Abu Balj, he said: I heard 'Amr ibn Maymun narrating from Abu Hurayrah, he said: The Messenger of Allah, peace and blessings of Allah be upon him, said to me: "Shall I not guide you to a word from the treasure of Paradise under the Throne: 'There is no power except by Allah' (La hawla wa la quwwata illa billah)?"