This article aims to elaborate on the pre-Ghazzālī period Sufis’ approaches to the concept of knowledge. We know that Ghazzālī, as a milestone in the Islamic thought, satisfies in taṣawwuf after a long quest. He benefits from the Sunnī taṣawwuf already established before him. Therefore, the importance of the sources feeding Ghazzālī’s Sufi view is manifest. Thus, in this article, I focus on the ideas of the main figures of the Sunnī taṣawwuf regarding the concept of knowledge. Having stated concisely about what taṣawwuf is, the concepts of knowledge and gnosis were described. And then, the ideas of the Sufis on knowledge and its ways were examined. I concluded at the end of the research that the Sufis restrict human reason (ʿaql) into the worldly life while giving the intuitional knowledge priority. Also, they separate the reality (ḥaqīqa) from religious law (sharīʿa). For the former, intuitional knowledge is a necessity, while the human reason is useful and responsible for the latter. Finally, it is hard to say that compared to Ghazzālī, Suhrawardī, and Ibn al-ʿArabī, those Sufis have a consistent epistemology when they set forth their view.