Chapter on Oaths, Vows, and Expiations
Man Lā Yaḥḍuruh al-Faqīh|Volume 3|Book 2|Chapter 38
وَ- قَالَ أَبُو أَيُّوبَ قَالَ أَبُو عَبْدِ اللَّهِ عَلَيْهِ اَلسَّلاَمُ مَنْ حَلَفَ بِاللَّهِ فَلْيَصْدُقْ وَ مَنْ لَمْ يَصْدُقْ فَلَيْسَ مِنَ اللَّهِ فِي شَيْءٍ وَ مَنْ حُلِفَ لَهُ بِاللَّهِ فَلْيَرْضَ وَ مَنْ لَمْ يَرْضَ فَلَيْسَ مِنَ اللَّهِ فِي شَيْءٍ.
Abu Ayyub said that Abu Abdillah عليه السلام said: "Whoever swears by Allah سبحانه وتعالى, let him speak the truth; and whoever does not speak the truth has nothing to do with Allah سبحانه وتعالى in any way. And whoever is sworn to by Allah سبحانه وتعالى, let him be content; and whoever is not content has nothing to do with Allah سبحانه وتعالى in any way."
- Ṣaḥīḥ al-Faqīh, p. 266