I stated, some time ago, that Imam Mahdi is the ultimate Islamic executive and that justice will prevail under his rule. This fact has also been reported in their sources: “Justice and liberty will prevail on Earth after it has been corrupted by tyranny and injustice.” I explained that the prophets did not fully accomplish their mission and thus he will come to finish their work (i. e. implementing justice worldwide). They (i. e. those clerics) wrongly interpreted my saying to mean that Imam Mahdi will complete the religion of Islam (which contradicts Islamic belief) thus serving the non-Muslim (world powers) whether intentionally or not. This is horrendous. Mahdi obeys Islam and follows the Prophet of Islam. But he is a follower whom the Prophet loved. He will implement his (peace be upon him and his progeny) directions.
Sahifeh, vol.13, Page: 84
Speech, August 12, 1980