Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) says: When the Messenger of Allah (peace and blessings be upon him) set out for the Battle of Hunayn, the people climbed onto the mounds and began saying the takbir in very loud voices. The Messenger of Allah (peace and blessings be upon him) said: "O people, recite your glorifications and takbirs softly; you are not calling upon one who is deaf or absent, rather you are calling upon One who is All-Hearing and Near, and He is with you." The narrator says: I was behind the Messenger of Allah (peace and blessings be upon him) and was saying: 'La hawla wa la quwwata illa billah' (There is no power and no strength except with Allah). He (peace and blessings be upon him) said: "O Abdullah bin Qays!" I said: Here I am, O Messenger of Allah! He (peace and blessings be upon him) said: "Shall I not tell you of a word that is from the treasures of Paradise?" I said: Of course, please do tell me! May my father and mother be ransomed for you. He (peace and blessings be upon him) said: "'La hawla wa la quwwata illa billah' is from the treasures of Paradise."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3012