Al-Kāfi - Volume 4 > Disciplines During Fasting
Hadith #4

4ـ عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ سَهْلِ بْنِ زِيَادٍ عَنِ الْحَسَنِ بْنِ مَحْبُوبٍ عَنْ أَبِي أَيُّوبَ عَنِ الْفُضَيْلِ بْنِ يَسَارٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلاَم) قَالَ إِذَا صَامَ أَحَدُكُمُ الثَّلاثَةَ الأَيَّامِ مِنَ الشَّهْرِ فَلا يُجَادِلَنَّ أَحَداً وَلا يَجْهَلْ وَلا يُسْرِعْ إِلَى الْحَلْفِ وَالأَيْمَانِ بِالله فَإِنْ جَهِلَ عَلَيْهِ أَحَدٌ فَلْيَتَحَمَّلْ.

4. A number of our people have narrated from Sahl ibn Ziyad from al-Hassan ibn Mahbub, from abu Ayyub, from al-Fudayl ibn Yasar who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said that if anyone of you fasts for three days of a month, you should not quarrel with anyone or act ignorantly. He should not be hasty to swear or to swear by Allah, and if anyone else may act ignorantly, he should exercise forbearance.”