Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 1522
Narated By Abu Musa al-Asha'ri : They (the Companions) accompanied the Prophet (pbuh) while they were climbing the turning of a hill. A man uttered loudly: "There is no god but Allah, and Allah is most great," when he ascended the hill. The Prophet of Allah (pbuh) said: You are not supplicating one who is deaf or absent. He then said: 'Abd Allah b. Qais. The narrator then transmitted a tradition to the same effect.