Al-Kāfi
Hadith 2153عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ أَبِي عَبْدِ اللَّهِ عَنْ عَلِيِّ بْنِ أَسْبَاطٍ عَنْ خَلَفٍ قَالَ رَآنِي أَبُو الْحَسَنِ ( عليه السلام ) بِخُرَاسَانَ وَ أَنَا أَشْتَكِي عَيْنِي فَقَالَ أَ لَا أَدُلُّكَ عَلَى شَيْءٍ إِنْ فَعَلْتَهُ لَمْ تَشْتَكِ عَيْنَكَ فَقُلْتُ بَلَى فَقَالَ خُذْ مِنْ أَظْفَارِكَ فِي كُلِّ خَمِيسٍ قَالَ فَفَعَلْتُ فَمَا اشْتَكَيْتُ عَيْنِي إِلَى يَوْمَ أَخْبَرْتُكَ .
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 (a.s.), 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.’”