Al-Kāfi

Hadith 196
worship
3ـ عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ سَهْلِ بْنِ زِيَادٍ عَنْ جَعْفَرِ بْنِ مُحَمَّدٍ الأشْعَرِيِّ عَنْ عَبْدِ الله بْنِ مَيْمُونٍ الْقَدَّاحِ عَنْ أَبِي عَبْدِ الله (عَلَيهِ السَّلام) قَالَ كَانَ أَمِيرُ الْمُؤْمِنِينَ (صَلَّى اللهُ عَلَيْهِ وآلِه) يَقُولُ أَفْضَلُ الْعِبَادَةِ الْعَفَافُ.
3. A number of our people have narrated from Sahl ibn Ziyad from Ja’far ibn Muhammad al-Ash’ari from ‘Abd Allah ibn Maymun al-Qaddah from Abu ‘Abdillah (a.s.) who has said the following: “Amir al-Mu’minin (Ali ibn abu Talib) (a.s.) would say, ‘Chastity is the best worship.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī