imam (a.s.) replied: goodness will be at that time when Mahdi emerges and will destroy such cruelties and oppressions.
the author of 'yanabi-ul-muwadda' narrates on page 491 from the book 'arba'een' of hafez abu na'eem isfahani that ali-ibn-abi talib (a.s.) said: 'i asked the messenger of Allah (s.a.w a.) as such: 'o messenger of Allah! is Mahdi from our progeny or from others?
the author of es'aaf-ur-raghebeen on page 151 has narrated from ahmad and maawardi a tradition from the messenger of Allah (s.a.w.a.) as follows:
'glad-tidings be to you about Mahdi. he is from the quraish and from my progeny who shall emerge at the time of discord and strife amongst the people....
'after me, shall come the caliphs. after the caliphs will come the rulers and after the rulers will come the kings. then oppressors will follow them and after them will emerge a man from my ahl-e-bayt who shall fill the earth with justice as it was filled with injustice....
the author of 'es'aaf-ul-raghebeen' has narrated (on page 148) a similar tradition from hakim.