Based on Chapter 20, what is the prerequisite for truly understanding profound scriptures like the Upanishads?

Chapter 20 strongly emphasizes that true comprehension of profound spiritual texts, such as the Upanishads, cannot be achieved through scholarly effort alone. The text states that the Upanishads are the essence of the Vedas and are "very difficult to grasp" without the grace of God and the Guru. The chapter warns that even a self-proclaimed scholar who tries to comprehend these texts by their own efforts will fail, as the path is "difficult at every step" without a Guru's grace. In contrast, for a devotee who is humble, detached, and attached to the Guru's feet, the hidden meanings of the scriptures open up automatically. This science of Self-knowledge is only accessible to the humble.