Chapter on Conditions and Options in Sales
Man Lā Yaḥḍuruh al-Faqīh|Volume 3|Book 2|Chapter 8
وَ رَوَى عَبْدُ اَللَّهِ بْنُ سِنَانٍ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: " اَلْمُسْلِمُونَ عِنْدَ شُرُوطِهِمْ إِلاَّ كُلَّ شَرْطٍ خَالَفَ، كِتَابَ اَللَّهِ عَزَّ وَ جَلَّ فَلاَ يَجُوزُ ".
Abdullah ibn Sinan narrated from Abu Abdillah عليه السلام who said: "Muslims are bound by their conditions, except for any condition that contradicts the Book of Allah سبحانه وتعالى, the Mighty and Exalted, which is not permissible."
- Ṣaḥīḥ al-Faqīh, p. 218