Sudair Sairafi narrates from Imam Sadiq (a.s.) (regarding Imam Mahdi (a.t.f.s.)), ‘…his prolonged disappearance will give rise to doubt and cynicism. People will cast all kinds of aspersions, and claim that he is not born as yet. Some others will declare that he was born but is not alive anymore. Some will say, the eleventh Imam was without any issue. Some claim that there are three entities. Some others make even more ridiculous claims and assert that Qaim’s soul resides in a different body, distinct from his own! All these disputes and aspersions on Mahdi are prohibited. Abdullah b. Masood has narrated this from the Prophet of Islam (s.a.w.s).’
Yanaabi al-Mawaddah chap 80 pg 116