Indeed Imam Mahdi (A.S) is the Guided one and Vice-regent of Allah (Khalifatullah)”. The Qaim (Mahdi “A.S”) will come to re-establish the lost sense of sanctity and integrity of the religion of Islam. Like the Holy prophet Muhammad (S.A.A.S) the just leader of mankind will also destroy that which was before, the rituals of the period of ignorance.
AS A BLESSING FROM ALLAH, HAZRAT MAHDI (AS) WILL BE EQUIPPED WITH SECRET KNOWLEDGE, SUCH AS ILM AL-LADUN Indeed: "The Mahdi will extract the Torah and the other Divine Books from their caverns and will judge amongst the faithful of the Evangiles according to the Evangiles, amongst the faithful of al-Zabur (The Book of David) according to the al-Zabur and amongst the faithful of the Quran according to the Quran.
The importance of al-Mahdi to Muslims and non-Muslims alike is that his appearance will have dramatic effects on the Muslims and the non-Muslims. As and when he appears the entire dynamics of this world will change as a result.
"al-Mahdi is from our Ahlul-Bayt, no doubt Allah will enforce his appearance within a night (i.e., his coming is very unpredictable and is very sudden)."
References: Sunan Ibn Majah, v2, p269
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