Imam Mahdi (AS) has said that if anybody were to narrate his sayings, he should compare the narrations with the Quran; if it is in conformity with the Quran, it is from him (the Imam). But if it is not conforming to the word of Allah, it is not from him (Imam Mahdi (AS)); may be the narrator could not comprehend his (the Imam's) sayings.
(Insaaf Nama - Matan Sharif N.11)
Imam Mahedi Ahs is quoted as having said that the sign of his confirmation (tasdiq) was that an impotent person becomes a potent man, that is, a seeker of the world became a seeker of Allah; a miser becomes a generous man, that is, a person who could not give even a dinar in charity, in the name of Allah, would give his life for the sake of Allah; an ummi (uneducated person) becomes an aalim (a learned man), that is, a person who did not know even a letter, becomes (so learned) that he would explain the meaning of Quran.
(Hashia Insaaf Nama - Hashia Sharif, N16)