Sahih al-Bukhari 7521

Narrated `Abdullah:Two person of Bani Thaqif and one from Quraish (or two persons from Quraish and one from Bani Thaqif) who had fat bellies but little wisdom, met near the Ka`ba. One of them said, "Did you see that Allah hears what we say? " The other said, "He hears us if we speak aloud, but He does not hear if we speak in stealthy quietness (softly)." The third fellow said, "If He hears when we speak aloud, then He surely hears us if we speak in stealthy quietness (softly)." So Allah revealed the Verse:-- 'And you have not been screening against yourselves, lest your ears, and your eyes and your skins should testify against you