In our article “JILA AL-BASAR LE MAN YATAWALLA AL-AIYEMME AL-ISNAESHAR” (glisten of sight to one who yields to the twelve Imams) we have dealt over this subject. The traditions that indicate that there are thirteen Imams are not authentic ones. The narration should be constant, that is, heard by many; hence, told by many or circulated mouth by mouth. Such narration of any tradition is gestant with credibility. If it is told by one person it does not stand credible.
When the Prophet (SAW) spoke, he spoke among his associates or in a gathering or amidst a few people. So, his conversation was heard by more than one man; and accordingly narrated by more than one. If a tradition is narrated by only one source and there is no second to it; it is void of any authenticity. This is a standard or a law for gaining certainty about the issue pertaining to belief and other religious matters. On the other hand, the traditions that indicate the number of Imams as twelve are many and related by several and told by various sources.
In the book MASNAD of Ahmad al-Hanbali there are above thirty sources mentioned having had heard from the Prophet (SAW) the number of Imams to be twelve. Muslim in his “SAHEER” quotes eight sources who have related the traditions indicating the number twelve. In the Shia books there are hundreds of sources who have mentioned the Prophet’s sayings the traditions, that fix the number of twelve. Besides, the sources form the man of good reputation. There remains no doubt in the authencity of the very subject. However the traditions or tradition quoting the number of Imams to be thirteen has been invented. Since it is a lie it is dismissed.