Abu’l Hijaf relates that the Prophet (saas) three times said: hear glad tidings about Hazrat Mahdi (as); he will appear when the people are fragmented and when troubles reveal themselves. He will fill the world that is filled with oppression and complaint with justice instead. He will install servitude to Allah in his servants’ hearts and his justice will surround everyone.
(Bihar Al Anwar, Vol. 51, p. 74)
And the Prophet (saas) also said, “HE [Hazrat Mahdi (as)] will fill a world full of oppression and complaint with justice instead.”
(Bihar Al- Anwar, Vol. 51, p. 66)
The hadith report that Hazrat Mahdi (as) will appear at a time when the world is filled with “complaint and oppression.” As a result of the climate of trouble and difficulty that Allah will create prior to the coming of Hazrat Mahdi (as), people will complain about everything. But Hazrat Mahdi (as) will put that away when he appears and by Allah’s leave, will bring peace, happiness, blessings and justice to all humanity.