Al-Kāfi

Hadith 201
worship
8ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنْ عَلِيِّ بْنِ الْحَكَمِ عَنْ سَيْفِ بْنِ عَمِيرَةَ عَنْ مَنْصُورِ بْنِ حَازِمٍ عَنْ أَبِي جَعْفَرٍ (عَلَيهِ السَّلام) قَالَ مَا مِنْ عِبَادَةٍ أَفْضَلَ عِنْدَ الله مِنْ عِفَّةِ بَطْنٍ وَفَرْجٍ.
8. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Ali ibn al-Hakam from Sayf ibn ‘Amirah from Mansur ibn Hazim from abu Ja’far (a.s.) who has said the following: “Abu Ja’far (a.s.) has said, ‘In the sight of Allah there is no worship more virtuous than chastity in matters of stomach and genital organs.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī