13. A number of our people have narrated from Ahmad ibn abu ‘Abd Allah from Ali ibn Asbat from Khalaf who has said the following: “Abu al-Hassan , saw me in Khurasan and I complained of eye trouble. He (the Imam) said, ‘May I teach you something which will remove your complaint because of your eyes?’ I replied, ‘Yes, I like to know it.’ He (the Imam) said, ‘Clip your fingernails every Thursday.’ I followed the instruction and have not complained ever since of my eyes.’”