Hazrat Mahdi (as) will be someone whose reason and faith are greatly to be trusted, and sincere people who recognize Hazrat Mahdi (as) will follow him

"O lord of the believers, inform us about your Mahdi (as)..." The lord of the believers said: "... He [HAZRAT MAHDI (AS)] IS THE BEST REFUGE, THE MOST KNOWLEDGEABLE, AND THE KINDEST OF YOU ALL. O’ Allah, make the pledge of allegiance to him the occasion of exit from affliction, AND UNITE THE DISPERSION OF THE UMMAH THROUGH HIM. When it is permissible for you, do it, BUT DO NOT TURN AWAY FROM HIM [HAZRAT MAHDI (AS)] if you find your way to him." (Kitab al-Ghayba, [Bihar al-Anwar, Vol. 51], Ansariyan Publications, Collected by: Muhammad Baqir Majlisi, Iran-Qum, 2003, p. 184)