Validation of Chains of Imam Reza's ilal ol-ahkam(causes of rules) letter with an emphasis on reliability analysis of Mohammad Ibn Sanan

Imam reza's correspondence in response to questions of Mohammad ibn Sanan al-zaheri about the explaining the causes of ordinances and laws has several chains that have raised in Uyun akhbar al-reza and Man la yahzoroho al-faqih books. These chains in basic and pure Rejali attitudes, due to weak narrators, seem to be invalid and weak, in addition to the weakness of the chains, the possibility of forgery correspondence by Mohammad ibn Sanan is also been raised. In this study, the critical assessment of weaknesses of the correspondence chains been discussed and reliability of narrators and the validity of these chains has been proved. The possibility of forging correspondence by Mohammad bin Sanan is also been rejected through conform with many of correspondence concepts with the same words and with phrases close to words in other ahl al-bayt traditions as well as the quotation of the correspondence by traditionists aware of the conditions of Mohammad ibn Sanan. After proving the validity of correspondence in rational manner that is based on avoiding the detailed conversations or correspondence on important and effective issues like explanation for causes and philosophy of Islamic rulings with an unreliable person and who are reputed to lie, this detailed and important correspondence is considered the discoverer of Imam confidence to this narrator and he accepted as a reliable narrator to the Shiite companions.