Mesbah Yazdi died on Friday evening at the age of 85 due to gastrointestinal disease, according to the semi-official ISNA news agency.

He had been hospitalized since Saturday after his condition deteriorated.  

Ayatollah Mesbah Yazdi played a major part in the uprising — led by late founder of the Islamic Republic Imam Khomeini — that overthrew the US-backed Pahlavi regime in 1979.

Following the Islamic Revolution, Ayatollah Mesbah Yazdi first founded Baqir-ul-Uloom Institute and then Imam Khomeini Education and Research Institute in the city of Qom, which he headed for the rest of his life.

The cleric, a philosopher and political theorist, was a member of the Society of Seminary Teachers of Qom.

He also served as a member of the Assembly of Experts —  the body responsible for electing and monitoring the performance of the Leader — and the Supreme Council of Cultural Revolution. The cleric was first hospitalized at home on December 4 in the city of Qom, but following the progression of his clinical symptoms, he was transferred to Tehran for further treatment. He died in hospital six days later.
In separate messages, Iranian President Hassan Rouhani and Parliament Speaker Mohmamad-Baqer Qalibaf offered condolences on the passing of Ayatollah Mesbah Yazdi.