Al-Kāfi
Hadith 2564ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنْ عَلِيِّ بْنِ الْحَكَمِ عَنْ مُوسَى بْنِ بَكْرٍ قَالَ لِكُلِّ شَيْءٍ زَكَاةٌ وَزَكَاةُ الأَجْسَادِ الصَّوْمُ.
4. 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.”