Musnad Ahmad 788:259

Abu Mu'awiyah narrated to us, he said: 'Asim al-Ahwal narrated to us, from Abu 'Uthman al-Nahdi, from Abu Musa, who said: We were with the Prophet, peace and blessings of Allah be upon him, on a journey. He said: So we descended into a valley of the earth. He said: Then the people raised their voices with the Takbir (saying Allahu Akbar). He said: "O people, be gentle with yourselves, for you are not calling upon one who is deaf, nor one who is absent. Indeed, you are calling upon One who is All-Hearing, Near." He said: Then he called me, and I was near him, and he said: "O 'Abdullah bin Qais, shall I not guide you to a word from the treasures of Paradise?" He said: I said: Yes. He said: "La hawla wa la quwwata illa billah (There is no power and no strength except by Allah)."