Jami` at-Tirmidhi 3248

Narrated Ibn Mas'ud:"Three men whose bellies were fat, but whose hearts had little understanding, were arguing at the House. Two of them were from Quraish and one was from Thaqif - or two from Thaqif, and one from Quraish. One of them said: 'Do you think that Allah can hear what we are saying?' Another said: 'He can hear if we are loud, but He can not hear when we are quiet.' Another said: 'If He can hear when we are loud then He can hear when we are quiet.' So Allah, the Mighty and Sublime revealed: And you have not been hiding yourselves, lest your ears and your eyes and your skins should testify against you (41:)