This study deals with the foundations that help understand [religious] texts from the viewpoint of Sayyid Muhammad Baqir al-Sadr. At first, an explanation is given in discussing the problem of understanding [religious] texts among Shiite scholars of Usul al-Fiqh, and among some Western hermeneutic scholars, in order to explore the most important fundamentals that they have set and the problems they have faced. After this, we turn to Shahid al-Sadr to see the rules he has put as a key to solving the problem of understanding [religious] texts. I have avoided lengthening, detailing and examples, especially when explaining the problem of understanding [religious] texts. Thus, I have followed an intensive manner in writing, referring readers to the sources I relied on, so that they might find whatever details and examples I have briefed. I did not assign a certain chapter for explaining the fundamentals of the West concerning the topic, but rather I referred very briefly to them here and there, because the goal of this article is to shed light on the rules of Sayyid Muhammad Biqir al-Sadr especially, mentioning six rules all together. I referred, in the footnotes, to some of their applications as mentioned in his own sayings.