A man from the tribe of Ati bin Damrah Sa'di falsely attributed himself to someone else, so Hazrat Abi (may Allah be pleased with him) shamed him by mentioning his father's private parts. People said to him, "You do not usually speak so openly?" He replied, "We have been commanded to do so, and the Noble Prophet (peace and blessings be upon him) commanded us that if you hear a man attributing himself to the lineage of ignorance, then shame him by mentioning his father's private parts."