Al-Kāfi - The Book of Fasting

Chapter: The Excellence of Fast and Fasting َّدُ بْنُ يَحْيَى عَنْ أَحْ٠َّدٍ عَنْ عَلِيِّ بْنِ الْحَكَ٠ُوسَى بْنِ بَكْرٍ قَالَ لِكُلِّ شَيْ‏ءٍ زَكَاةٌ وَزَكَاةُ الأَجْسَادِ الصَّوْ٠4.

Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Ali ibn al-Hakam from Musa ibn Bakr who has said the following: “He (the Imam) (a.s.), said, ‘Everything has a cleanser; the cleanser for bodies is fasting.” عتبر - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (16/199))