Sayyiduna Hazim bin Harmalah (may Allah be pleased with him) narrated: One day I was passing by when the Messenger of Allah (peace and blessings be upon him) called me. I came to him (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Say 'La hawla wa la quwwata illa billah' (There is no might and no power except with Allah) often, for it is one of the treasures of Paradise."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3552