Al-Lu'lu Wal-Marjan 1768 — The Book About the Characteristics of the Hypocrites and Orders Concerning Them.

'Abdullah bin Mas'ud Narrated from:

There gathered near the House (i.e. the Ka’ba) two Quraishî persons and a person from Thaqîf (or two persons from Thaqîf and one from Quraish), and all of them with very fat bellies but very little intelligence. One of them said, “Do you think that Allâh hears what we say?” Another said, “He hears us when we talk in a loud voice, but He doesn’t hear us when we talk in a hidden low voice." The third said, "If He can hear when we talk in a loud voice, then He can also hear when we speak in a low voice."Then Allâh, the Honourable, the Majestic revealed: 'And you have not been hiding against yourself, lest your ears, and your eyes, and your skins should testify against you....' (V.41:22,23)( Sahîh Al-Bukhâri, Hadîth No. 341, Vol. 6)