ʿIlal al-sharāyiʿ (literally: reasons of the rulings) is an Arabic book written by al-Shaykh al-Saduq (d. 381/991) who was a great jurist (faqih) and hadith scholars of Shi’a in fourth/tenth century.
The book contains narrations from the Prophet (s) and Imams (a) regarding the reasons of religious obligations and theological beliefs. It also includes the reason of naming some characters and events and some information about creation of animals. Al-Shaykh al-Saduq mentioned some points on the behaviors and activities of the Prophet (s) and Imams (a).
The book has been published in two volumes and has 647 chapters. It is a reliable book and Shi’a scholars trusted it.