“It is about the case of a woman before abu ‘Abd Allah (a.s.), when a man asked him (the Imam) about a man against whom his wife alleges that he is impotent but the man denies it, abu ‘Abd Allah (a.s.), said, ‘She must allow the nurse to fill her with al-Khaluq (a certain perfume) without allowing the man to know. He then goes to bed with her; if perfume is found on his penis he has told the truth, otherwise, she has spoken the truth and he has lied.’”