Sunan Ibn Majah Book 33, Hadith 168
"The Prophet (saas) heard me saying: 'La hawla wa la quwwata illa billah (there is no power and no strength except with Allah).' He said: 'O 'Abdullah bin Qais! Shall I not tell you of a word which is one of the treasures of Paradise?' I said: 'Yes, O Messenger of Allah.' He said: 'Say: La hawla wa la quwwata illa billah (There is no power and no strength except with Allah).'"
of Allah (saas) said: "Every deed of the son of Adam will be multiplied for him, between ten and seven hundred times for each merit. Allah said: 'Except for fasting, for it is for Me and I shall reward for it.'" (sahih)
"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)