Man Lā Yaḥḍuruh al-Faqīh #648"Muslims are bound by their conditions, except for any condition that contradicts the Book of Allah (swt), the Mighty and Exalted, which is...
Mīzān al-Ḥikma #816The Prophet (SAWA) said, ‘Muslims [make and] fulfil their promises according to what is permissible.