The main subject of the present research is to evaluate the methodological approach and application of the discussions of the science of Usul al-Fiqh, especially the discourse of words such as the derivative (mushtaq) and the present tense verb, in the article “The Significance of the Verse La Yanal in Proving the Infallibility of Prophets,” which is organized based on an analytical-critical method with the aim of demonstrating the extent of the strength of the result mentioned in the mentioned article. The most important achievements of the current research are showing the author’s lack of attention to all aspects that affect the inference from the verse La Yanal (Al-Baqarah: 124) - such as: adding the meaning of the derivative to the analysis of the meaning of the present tense verb, and explaining the text or the apparent meaning of the derivative on the exclusivity of the true meaning in the essence characterized by the origin - in a way that if such attention were paid, the verse’s indication of the absolute infallibility of the prophets would be acknowledged. The author’s non-adherence to his claim to avoid imposing a premise in the analysis of the verse, as well as the inconsistency of some of the content with the author’s chosen foundations, and the failure to analyze the relationship between the two concepts of injustice and justice, are among the influential factors in the incorrect inference from the verse La Yanal in the mentioned article.