Al-Kāfi - Volume 6 > Wudu (washing hands clean) before and after Food
Hadith #3

مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ الْقَاسِمِ بْنِ يَحْيَى عَنْ جَدِّهِ الْحَسَنِ بْنِ رَاشِدٍ عَنْ أَبِي بَصِيرٍ عَنْ أَبِي عَبْدِ اللَّهِ ( عليه السلام ) قَالَ قَالَ أَمِيرُ الْمُؤْمِنِينَ ( عليه السلام ) غَسْلُ الْيَدَيْنِ قَبْلَ الطَّعَامِ وَ بَعْدَهُ زِيَادَةٌ فِي الْعُمُرِ وَ إِمَاطَةٌ لِلْغَمَرِ عَنِ الثِّيَابِ وَ يَجْلُو الْبَصَرَ .

3. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from al-Qasim ibn Yahya from his grandfather Hisham ibn Salim ibn Rashid from abu Basir who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said that ’Amir al-Mu’minin has said, ‘Washing hands before and after eating food removes stains from clothes and clears eyesight.’”