Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: Once I was hidden in the curtain of the Ka'bah. In the mosque (that is, near the Ka'bah) there was a man from the tribe of Thaqif and his two sons-in-law who belonged to the Quraysh. They said: What do you think? Does Allah Almighty hear our conversation? One of them said: If we speak loudly, then He will hear. The second said: If He can hear when we speak loudly, then He should certainly hear when we speak softly as well. The third said: I think that Allah Almighty hears everything we say. Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: I went to the service of the Prophet (peace and blessings be upon him) and informed him about what those people had said, so Allah Almighty revealed this verse: "And whatever you conceal, your hearing and your sight will bear witness against you."