From ‘Utay ibn Damra who said: I saw a man with Ubayy who was boasting of greatness [i.e. lineage] going back to the age of ignorance [jahiliyya], and Ubayy made him bite – without mincing words with him. His companions looked at him and he said: It seems you all disprove of that? And he said: I will never respect anyone in this regard; indeed I heard the Prophet (SAW) say: Whoever boasts of greatness going back to the age of ignorance, tell him to go bite [a’idduhu]* – without mincing words.
* “Tell him to go bite” : In another narrative, Ahmad and others added “his father’s thing [han]”. Ibn Al-Athir said: In other words, tell him “Go bite your father’s dick [ayr]”, and do not mince words by saying “thing” instead of “dick”, so that it serves as a lesson and discipline to him.