سنن ابن ماجه

It was narrated that Abu Dharr said: "The Messenger of Allah (saas) said to me: "Shall I not tell you of a treasure which is one of the treasures of Paradise?' I said: 'Yes, O Messenger of Allah.' He said: 'La hawla wa la quwwata illa billah (There is no power and no strength except with Allah).'" (sahih)