Hazrat Mahdi (as) will purge the subsequent bi'dah (innovations) in Islam and guide people to live by the Qur'an and the Sunnah of our Prophet (saas)

WHEN PEOPLE INTERPRET THE QUR’AN ACCORDING TO THEIR OWN LOWER SELVES, HAZRAT MAHDI (AS) WILL CORRECTLY TURN THEIR THOUGHTS TO THE QUR’AN AND PLACE THEM UNDER THE SERVICE  OF TRUTHS OF THE QUR’AN. AFTER THAT HE WILL SHOW YOU HOW THE BOOK AND THE SUNNAH HAVE BEEN FORGOTTEN AND REVEAL THEIR LIVING MEANINGS. Nehcü’l Belağa, sermon 134.

In the End Times, when Hazrat Mahdi (as) appears, some people will interpret the Qur’an according to their own lower desires and interests, and will seek to turn people toward these interpretations. But Hazrat Mahdi (as) will reveal the true meanings of the verses of the Qur’an. In this time, when people have spiritually turned away from the verses of the Qur’an and the Sunnah of our Prophet (saas), he will expound the true meaning of the verses.