Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: "I was hiding behind the coverings of the Ka'bah when three men came: a man of Thaqif and his two sons-in-law of Quraysh, whose bellies were full of fat but whose understanding was little. They talked among themselves, and one of them said: 'Do you think Allah hears what we say?' Another said: 'When we speak aloud He hears, and when we speak quietly He does not hear.' The third said: 'If He hears when we speak aloud, then He will also hear when we speak quietly.' So I came to the Prophet (peace and blessings be upon him) and mentioned that to him, and Allah, the Mighty and Majestic, revealed this verse: 'And you were not concealing yourselves lest your hearing, your sight and your skins should testify against you, but you assumed that Allah does not know much of what you do' [Surah Fussilat: 22] up to 'among the losers' [Surah Fussilat: 23]."
Sufyan al-Thawri narrated it in this way, while Abu Mu'awiyah and the other students of al-A'mash differed from him.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10096