Imam Husain b. Ali (a.s.) informed, ‘There are twelve Mahdis (divinely guided ones) among us. The first one is Ameerul Momineen – Ali b. Abi Talib (a.s.). The last one is my ninth descendant who is the Riser for the Truth. Allah will revive the earth through him after it perishes, and will make the True Religion victorious over all religions through him, even though the atheists may not like this.’
Oyoon Akhbaar al-Reza (a.s.) chap 6 trad 36