This research deals with an important fundamental issue in the field of inference, which is the authenticity of Isolated Hadith and how to deal with it in legal rulings and doctrinal investigations; Many issues have been raised about it. The research aims to reveal and clarify this issue. Presenting and analyzing it according to the inferences of Sunni scholars in general, and shedding light on it according to the inferences and method of Imam Muhammad bin Ismail al-Bukhari; To clearly show the features of the fundamentalist school, which Al-Bukhari considers one of its most prominent figures, and he has a distinguished fundamentalist approach in that, which is characterized by accuracy and care. As an attempt to explain Al-Bukhari’s approach to inference for one of the fundamental issues that are still in dispute between the sects, the study was based on Al-Bukhari’s reports on this issue; and its applications in his books, with a statement of the reason for its inference, to conclude a satisfactory scientific result; It agrees with Al-Bukhari’s approach and its inferences in explaining the authenticity of the Isolated Hadith and its necessity in receiving and inference.