Throughout the history of the transmission of the hadith, there are many Sanads in which the names of the narrators are mentioned in such a way that has caused the confuse of them with other narrators or to consider them unknown. This issue is so widespread that it has formed one of the most important branches in the science of Rijal, namely, Tamyyiz Mushtarekat & Tawhid Mukhtalefat. Much attention has been paid to this issue in the Shia and Sunni sources, but one of the most important issues in this regard is the full knowledge of the criteria that should be used in this process. This article, for example, focuses on the names used for Muhammad ibn 'Umar Ji'abi, one of the greatest narrators, and at the same time, It states the criteria that can guide this process. To be more methodical. The most important of these criteria are: the date of birth and death of the narrator, his teacher and student in the Sanad, the tradition of brevity in mentioning the lineage of persons, distortion in the narrators' names, the tendency of some narrators to Using different terms and refraining from mentioning masters uniformity, Tadlis and attention to the attribution of narrators to different places.