He has written many works in the fields of theology and tafsir. For his great contributions and tremendous influence, he received the honorable title of al-Shaykh al-tāifa (the chief or head of the Shi'a).
He moved from Khurasan to Iraq at the age of 23 and benefited from professors such as al-Shaykh al-Mufid and al-Sharif al-Murtada.
Life
He was born in Khorasan in Ramadan , four years after the demise of al-Shaykh al-Saduq and the same year of the demise of Harun b. Musa Talla'ukbari. His kunya was Abu Ja'far and since the kunya of both al-Shaykh al-Kulayniand al-Shaykh al-Saduq also was Abu Ja'far, he is sometimes called the third Abu Ja'far.
Al-Shaykh al-Tusi spent the first part of his life in Khorasan, and moved to Baghdad at the age of 23. In Baghdad, he studied under leading Shi'a scholars such as al-Shaykh al-Mufid, al-Sharif al-Murtada, and Ibn al-Ghada'iri. The Abbasid caliph of the time eventually appointed him to the principal chair of theology in Baghdad, where nearly three-hundred students would attend his classes.
Following the demise of al-Sharif al-Murtada, al-Shaykh al-Tusi took over the leadership of the Shi'a.
After his house and library were burnt down in the sectarian conflicts , and the decline of the Buyid dynasty, al-Shaykh al-Tusi moved to Najaf. There, he established a Shi'i scholarly circle which led to the formation of the Islamic Seminary of Najaf.
Scholarly Position
Al-Shaykh al-Tusi was the leader of Shi'a faqihs. He attained the station of ijtihad in both fiqh and usul al-fiqh. From the Four Books, al-Shaykh al-Tusi is the author of both al-Istibsar and Tahdhib al-ahkam.
The ideas and works of al-Shaykh al-Tusi had overshadowed Shi'a scholarship and no one opposed his opinions until the time of Ibn Idris. His book, al-Nihaya, was the main source of teaching in Shi'a scholarly circles until al-Muhaqiq al-Hilli wrote Shara'i' al-Islam.
Al-Shaykh al-Tusi wrote in nearly all fields of Islamic sciences. His works are a unique resource for later generations because many of the sources he used were destroyed when Shapur library was burned.
Teachers
Al-Tusi studied with many teachers, but the following five figures are the ones he refers to most:
• Abu 'Abd Allah Ahmad ben 'Abd al-Wahid ben Ahmad al-Bazzaz, known as Ibn Hashir
•Ahmad ben Muhammad ben Musa, known as Ibn Salt al-Ahwazi.
•Abu 'Abd Allah al-Husayn ben 'Ubayd Allah b. al-Ghada'iri .
•Abu l-Husayn 'Ali ben Ahmad ben Muhammad ben Abi Jayd al-Qummi.
•Abu 'Abd Allah Muhammad ben Muhammad ben Nu'man, known as al-Shaykh al-Mufid .
List of Students of al-Shaykh al-Tusi
It is reported that al-Tusi had over 300 Shi'ite students, and many other Sunni ones. The most well-known of them are Abu l-Salah al-Halabi, a prominent faqih and theologian and the author of al-Kafi fi l-fiqh; Muhammad ben 'Ali al-Karajuki, the author of Kanz al-fawa'id; and his son al-Hasan ben Muhammad al-Tusi, known as "al-Mufid al-Thani".
Works
Al-Shaykh al-Tusi composed over fifty books in the fields of fiqh, hadith, theology, and tafsir. Some of his important works are as follows:
• Al-Istibsar fi ma ukhtulif min al-akhbar: This compilation of hadith is one of the Four Books and one of the main sources of Shi'a fiqh.
• Al-Tibyan fi tafsir al-Qur'an : This book is the first commentary of the Qur'an which compiles all aspects of 'Ulum al-Qur'an.
•Tahdhib al-ahkam: This hadith compilation is one of the Four books.
•Misbah al-mutuhajjid: This is one of the most important and reliable Shi'a resources for rituals, practices, and prayers.
• Al-'Uddat fi l-usul: The first part of this book is about usul al-din (the principles of faith), and the second is about usul al-fiqh (the principles of fiqh).
Thoughts and Intellectual and Religious Position
Al-Shaykh al-Tusi was among the leaders of intellectualism in Baghdad and followed the method of his teachers, al-Sayyid al-Murtada and al-Shaykh al-Mufid and perfected it. Al-Shaykh al-Tusi wrote books in different branches of religious studies and since he was influential in Shi'a society and had many students, could make a lasting influence over Shi'a scholars. Ijtihad and intellectualism in Shi'a fiqh and beliefs prevailed among Shi'a due to the efforts of al-Shaykh al-Tusi who ended the dominance of several centuries of Akhbarism.
Establishment of the Seminary of Najaf
After the invasion of Seljuk Turks to Baghdad and its following events like burning of the Shapur library and the fight between Shi'a and Sunnis in Baghdad, al-Shaykh moved to Baghdad and began his scientific activity in that city and the great seminary of Najaf was established due to his efforts. Al-Shaykh could bring order to disordered educational situation in Najaf and hold study circles. Few people who had either accompanied Shaykh to Najaf or had heard his fame, joined him and soon Najaf became the intellectual and scientific center of Shi'a. However, some believe that study circles were formed before Shaykh went to Najaf and his role was to bring order and stability to the seminary of Najaf.
The Role of al-Shaykh al-Tusi in Perfection of Shi'a Fiqh
Introducing intellectual and discursive method for understanding the rulings of fiqh is usually considered as the most prominent achievement of al-Shaykh al-Tusi in the history of Shi'a fiqh. Before al-Shaykh al-Tusi, the prevalent method in fiqh was hadith-oriented. In al-Mabsut, al-Shaykh al-Tusi benefitted from ijtihad approach to understand rulings from hadiths based on the usuli principles. Al-Shaykh al-Tusi's method had a great influence over the historical course of Shi'a fiqh and it was unrivaled among Shi'a faqihs for ages later.
Innovation in Writing Commentary on the Qur'an
Al-Shaykh al-Tusi is the author of al-Tibyan fi tafsir al-Qur'an, which was a model for later Shi'a commentaries. It is the first complete commentary of the Qur'anwritten by a Shi'a and includes all the chapters of the Qur'an. It is distinguished from previous commentaries because in al-Tibyan, al-Shaykh al-Tusi considered the opinions of other Shi'a and Sunni scholars, discussed about the opinions of other exegetes, benefitted from pre-Islamic Arabic literature, gave information on difficult words of the Qur'an and mentioned the differences among recitations and issues in fiqh, theology, and rhetorics in verses of the Qur'an. Shi'a commentaries before al-Shaykh al-Tusi only mentioned hadiths about the verses of the Qur'an.
The most important feature of al-Shaykh al-Tusi's method in exegesis was his ijtihad and intellectualism in interpretations of the Qur'an which made it different from simple hadith-oriented approach of previous exegetes. Al-Shaykh al-Tusi brought proofs from the verses of the Qur'an that the Qur'an is an understandable text for human intellect and did not accept hadiths which considered referring to hadiths as the only way to understand the Qur'an.
Demise
Al-Shaykh al-Tusi lived for 12 years in Najaf and passed away in Muharram. According to al-Shaykh's will, he was buried in his house, and the house was converted into a mosque. The al-Shaykh al-Tusi mosque, which is also called Jami' al-Shaykh al-Tusi, is one of the most famous mosques of Najaf. It has been reconstructed and repaired several times, and is used by the professors and scholars of the Islamic Seminary of Najaf as a place for holding lectures.