The development of the ta'ziah—a passion play commemorating the martyrdom of Imam Husayn and his family — and Ziarat of the shrines and tombs of local Shi'ite leaders began during this period, largely at the prompting of the Shi'ite clergy.[29] According to Mortaza Motahhari, the majority of Iranians turned to Shi'a Islam from the Safavid period onwards. Of course, it cannot be denied that Iran's environment was more favorable to the flourishing of the Shi'a Islam as compared to all other parts of the Muslim world. Shi'a Islam did not penetrate any land to the extent that it gradually could in Iran.