Musnad Ahmad 944:0

Narrated to us by Muhammad ibn Ja’far, who said: Narrated to us Shu’bah, from ‘Amr ibn Murrah, who said: I heard Murrah al-Hamadani narrating from Khuzaymah ibn Thabit, from the Prophet (ﷺ), who said: "Verily, Allah is not ashamed of the truth. Do not be ashamed to ask about anything, even if it is about the anus." He said: And he mentioned something else, but I do not remember it.