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, whose bellies were full of fat but whose hearts had little understanding: a man of Quraysh and his two sons-in-law of Thaqif, or a man of Thaqif and his two sons-in-law of Quraysh. They spoke words that I could not understand. One of them said: 'Do you think Allah hears our speech?' Another said: 'When we raise our voices He hears them, and when we do not raise them He does not hear them.' The third said: 'If He hears any of it, He hears all of it.' So I mentioned that to the Messenger of Allah (peace and blessings be upon him), and Allah, the Mighty and Majestic, revealed this verse: 'And you were not concealing yourselves lest your hearing and your sight should testify against you' [Surah Fussilat: 22], the complete verse."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10098