One of the reasons for proving the birth and existence of the revered ' Hojjate-ebn-al-hasanal-askari' (Mahdi) is the Hadiths (Prophet Words) cited repeatedly by both Shi' a and Sunni and in that prophet reiterated the number of his successors as twelve. These Hadiths are named 12-Imam or Calife Hadiths for brevity. In some Hadiths by Sunnis and Shi' as, the attributes and qualities of these successors are also described in addition to their number.Of the noteworthy points in these citations is the introduction of the end of these twelve successors and the news of his occultation. In them, the father and the ancestor of this person is clarified. These Hadiths indicate the birth and existence of the revered Hojjat in two ways: firstly in general, by reasoning about the figure of twelve and its agreement among both Shi' a and Sunni. Then, by text, where reasoning is made about the attributes and qualities [of the Mahdi], as cited in the religious citations, about the twelfth Imam, who is alive.Ahmad Katib, the author of the book ' al- Imamal-Mahdi: Haghigha Tarikhia am Farziata Falsafia' publishe in 2007 (Imam Mahdi: The Historical Truth or Philosophical Hypothesis) who attempts to deny the existence of Twelfth Imam, raises ambiguities about the Hadiths of twelve Imam in pages 127-133 of his book. Summarily, he holds that these beliefs and Hadiths are fake and were forged in the 4th century (of Hejira Calendar) so they are not valid references.In this issue, the alst section of his claims in this regard is cited and critiques.Summary of the Ambiguities: Sheikh Mofid has enfeebled the book of Salim The doubts of Zeidiya about the Hadiths about Twelve Imams.The Hadiths about Twelve Imams does not stipulate the existence of the son of Imam Hassan- el Askari.Summary of replies [to the above Ambiguities]: There is a wrong inference from Sheikh Mofid' s words: he warns common people, not enfeeblement of expression Sheikh Saduq has replied all the doubts of Zeidiyyeh, but the author haven' t mentioned them The Hadiths about Twelve Imams stipulate in two manners: one to the generals and the other to the text.