Abu Hamza says: “I asked Imam Sadiq, “CAN THE WORLD REMAIN PERMANENT WITH NO IMAM [HAZRAT MAHDI (AS)]?” THE IMAM SAID, “IF THE EARTH IS LEFT WITHOUT AN IMAM THERE WILL BE TOTAL UPHEAVAL.” (Usul al-Kafi, Islamiya edition, 1381, Vol. 1, p. 334) |
Washa says: “I asked Imam Riza (as), “Can the world be left with no imam?” The imam (as) answered, “No,” and then went on to say, “the world cannot be left with no imam, otherwise there will be complete upheaval.” (Usul al-Kafi, Vol. 1, p. 334) |
Mufazzal bin Omar, commander of the faithful: He spoke from the pulpit in the city of Qufa: “KNOW THAT THE EARTH CANNOT SURVIVE IN THE ABSENCE OF THE HUJJAT [HAZRAT MAHDI (AS)] OF ALLAH... IF ALLAH SUDDENLY TAKES THE HUJJAT [HAZRAT MAHDI (AS)] AWAY, THE EARTH WILL COLLAPSE OVER PEOPLE.” (Sheikh Muhammad bin Ibrahim Nomani, al-Ghaybah al-Nomani, p. 162) |

Bediuzzaman Said Nursi also notes this attribute of Hazrat Mahdi (as) in his works:
His (the Mahdi’s) Second duty: To resuscitate the essence of the moral values of Islam with this title of the caliph of Muhammad (in other words as Muslims’ spiritual leader). To make the union of the Islamic world his foundation and TO SAVE MANKIND FROM MATERIAL AND SPIRITUAL DANGERS AND FROM THE WRATH OF ALLAH... (Emirdag Addendum, p. 259) |
According to Bediuzzaman's account, as the spiritual leader of the Islamic world, Hazrat Mahdi (as) will free mankind, which is suffering from the corruption and disorder of the End Times, from all physical and spiritual dangers, and will teach people to avoid the wrath of Allah and will thus be instrumental in their salvation in this world and in the Hereafter.