Merits Of The Rule Of Imam Mahdi (A.S.)
 
Amirul Momineen Ali (A.S.) said,

"He will direct desires towards (the path of) guidance while people will have turned guidance towards desires, and he will turn their views to the direction of the Quran while the people will have turned the Quran to their views."
(Nahjut Balagha, sermon no, 138)
According to the submission of Ibne Abil Hadid, this saying refers to Hazrat Mahdi (A.S.) 
(Sharhe Nafyul Balagha vol.9. Pg.40) 

Imam Jafar as-Sadiq (A.S.) said,

"When the Qaem shall arise, he will rule with justice, the tyrants of his time shall fear him, the righteous will be safe, the earth shall reveal its treasures, all the truth-seekers will seek his company and no follower of any religion would remain except that they see Islam and declare their faith in it."
(Kashful Ghumma vol.3. Pg.255)

Imam Raza (A.S.) said,
"The fourth of my descendants is the son of the chaste maid. Allah shall purify the earth from every atrocity through him and rid it of every injustice. He is the one whose birth shall be doubted. He will have an occupation before his reappearance. When he reappears, the earth will light up with his brilliance. And he will establish the scales of justice among the people. Then, (among men), one will not oppress the other."
(Faraidus Simtain vol.2. Pg.336)