Grand Ayatollah Fazel Lankarani was declared as the most knowledgeable specialist in the field of Islamic law (Marja al-taqlid) by the central Shi'a school of religious studies in Qom, Hawza 'Ilmiyyah, after the death of Ayatollah Khomeini. At the time of his death, he was one of seven Grand Ayatollahs in Iran. His Resalah, the book including his interpretation of Islamic laws on different topics, is available in Arabic, English, Persian, Turkish, and other languages. Lankarani taught in the areas of the interpretation of Islamic law (fiqh) and Usul al-fiqh for the last 25 years of his life.