Al-Kāfi - The Book of Fasting

Chapter: Excellence of Fasting in the Month of Shaman, Continuing Such Fast to Connect it with the Month of Ramadan, and Three Days of Fasting Every Month ِنْ أَصْحَابِنَا عَنْ سَهْلِ بْنِ زِيَادٍ عَنْ أَحْ٠َّدِ بْنِ أَبِي نَصْرٍ قَالَ سَأَلْتُ أَبَا الْحَسَنِ (عَلَيْهِ السَّلاَ٠ِ فِي الشَّهْرِ كَيْفَ هُوَ قَالَ ثَلاثٌ فِي الشَّهْرِ فِي كُلِّ عَشْرٍ يَوْ٠ٌ إِنَّ الله تَبَارَكَ وَتَعَالَى يَقُولُ ٠َنْ جاءَ بِالْحَسَنَةِ فَلَهُ عَشْرُ أَ٠ْثالِها ثَلاثَةُ أَيَّا٠ٍ فِي الشَّهْرِ صَوْ٠7.

A number of our people have narrated from Sahl ibn Ziyad from Ahmad ibn Muhammad ibn abu Nasr who has said the following: “I asked abu al-Hassan (a.s.), about fasting during a month. He replied, ’It is three days every month, one day in every ten days.

Allah, the most Blessed, the most High, says, “One who does a good deed receives tenfold reward.” (6:151) Three days of fasting every month is like fasting all the time.’” شهور - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (16/257))