Al-Kāfi - Volume 6 > Eating with the Right Hand
Hadith #2

أَحْمَدُ بْنُ مُحَمَّدٍ عَنِ الْحُسَيْنِ عَنِ الْقَاسِمِ بْنِ مُحَمَّدٍ عَنْ عَلِيِّ بْنِ أَبِي حَمْزَةَ عَنْ أَبِي بَصِيرٍ عَنْ أَبِي عَبْدِ اللَّهِ ( عليه السلام ) قَالَ لَا تَأْكُلْ بِالْيَسَارِ وَ أَنْتَ تَسْتَطِيعُ .

2. Ahmad ibn Muhammad has narrated from al-Husayn, from al-Qasim ibn Muhammad from Ali ibn abu Hamzah from abu Basir who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘Do not eat with your left hand if you can.’”