Musnad Ahmad 788:36

Waki’ narrated to us, from Sufyan, from ‘Asim—meaning al-Ahwal—from Abu ‘Uthman, from Abu Musa, who said: We were with the Messenger of Allah, peace and blessings of Allah be upon him, on a journey. We overlooked a valley, and he mentioned its terror, so the people began to proclaim the greatness of Allah (Takbir) and the oneness of Allah (Tahlil). The Prophet, peace and blessings of Allah be upon him, said: "O people, be gentle with yourselves." And they raised their voices. He said: "O people, you are not calling upon one who is deaf, nor one who is absent. Indeed, He is with you."