Najm ul-Din Abul-Qasim Ja'far bin al-Hasan bin Yahya bin al-Hasan bin Sa'id, famous as al-Muhaqqiq al-Hilli and al-Muhaqqiq al-Awwal (c. 1205 – 1277)[1] was an influential Arab Shi'i Mujtahid born in the city of al-Hilla, Iraq. He played an important role in shaping Twelver Shi'ism's legal doctrines works. His legal manual, Shara'i ul-Islam, has been particularly influential, attracting more than thirty commentaries.