Al-Kāfi - Volume 4 > The Excellence of Fast and Fasting
Hadith #2

2ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنْ عَبْدِ الله بْنِ الْمُغِيرَةِ عَنْ إِسْمَاعِيلَ بْنِ أَبِي زِيَادٍ عَنْ أَبِي عَبْدِ الله عَنْ آبَائِهِ (عَلَيْهِم السَّلاَم) أَنَّ النَّبِيَّ (صلَّى اللهُ عَلَيْهِ وَآلِه) قَالَ لأَصْحَابِهِ أَ لا أُخْبِرُكُمْ بِشَيْ‏ءٍ إِنْ أَنْتُمْ فَعَلْتُمُوهُ تَبَاعَدَ الشَّيْطَانُ مِنْكُمْ كَمَا تَبَاعَدَ الْمَشْرِقُ مِنَ الْمَغْرِبِ قَالُوا بَلَى قَالَ الصَّوْمُ يُسَوِّدُ وَجْهَهُ وَالصَّدَقَةُ تَكْسِرُ ظَهْرَهُ وَالْحُبُّ فِي الله وَالْمُوَازَرَةُ عَلَى الْعَمَلِ الصَّالِحِ يَقْطَعُ دَابِرَهُ وَالاسْتِغْفَارُ يَقْطَعُ وَتِينَهُ وَلِكُلِّ شَيْ‏ءٍ زَكَاةٌ وَزَكَاةُ الأَبْدَانِ الصِّيَامُ.

2. Ali ibn Ibrahim has narrated from his father, from ‘ Abd Allah ibn al-Mughirah from Isma‘il ibn abu Ziyad who have said the following: “Abu ‘Abd Allah, has narrated from his ancestors, ‘Alayhim al-Salam, who have stated this Hadith. ‘Once, the Holy Prophet, O Allah, grant compensation to Muhammad and his family worthy of their services to Your cause, asked his companions, ‘Should I tell you something which, if you do it, will keep Satan away from you as far as east and west?’ They replied, ‘Please do so.’ The Holy Prophet said, ‘Fasting turns Satan’s face black, charity breaks his back, love for the sake of Allah and supporting good deeds cuts off his tail (followers), and asking forgiveness cuts off his artery. Everything has a zakat (cleanser). Zakat of the bodies is fasting.’”