Hujjat al-Islam (also Hojatoleslam) is an honorific title meaning “authority on Islam” or “proof of Islam”.
In Sunni tradition, the title is used exclusively for the scholar al-Ghazali, due to his influential integration of Sufism and sharia.
In Twelver Shia the title is awarded to scholars. It was originally applied as an honorific to leading scholars, but now the use indicates a status in the hierarchy of the learned below Ayatollah. It is divided into two sub ranks, Hujjatu l-Islām wa l-Muslimīn (“Authority on Islam and Muslims”) and Hujjatu l-Islām (“Authority on Islam”), given to middle-ranking clerics.
Hawza students start their studies learning fiqh, kalam, hadith, tafsir, philosophy and Arabic literature. After mastering these levels they are given the Hojatoleslam title, and can start becoming mujtahid by studying advanced textbooks known as satḥ, and research courses known as kharij.