Prophet Muhammad (peace be upon him and his progeny) informed his companion Jabir ibn Abdullah Al Ansari (May Allah’s mercy be on him)
“Mahdi is from my descendants. His name is my name and his agnomen (Kunniyat) is my agnomen. He most closely resembles me in appearance and behavior than all other people. There will be occultation and confusion for him. So much so that people will deviate from their religion. Then a time will come when he will appear like a shooting star and he will fill up the earth with equity and justice just as it will be filled with injustice and oppression.”
Kamaluddin Wa Tamamun Nemah, Vol 1 page 300