It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that two men brought their dispute to the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) asked the claimant for witnesses, but he had no witnesses. Therefore, the Prophet (peace and blessings be upon him) demanded an oath from the defendant. He swore, "By Allah, besides whom there is no deity, I do not have anything." Meanwhile, Hazrat Jibreel (peace be upon him) came and said, "This person is lying; he does have the right of the other. Therefore, order him to give that right, and the expiation for his false oath is the recognition and testimony of 'La ilaha illallah' (There is no god but Allah)."