According to the text, what is the importance of a Guru in understanding profound scriptures like the Upanishads?

Chapter 20 strongly emphasizes the indispensable role of a Guru for spiritual understanding. The text explains that the Upanishads contain the essence of the Vedas but are incredibly difficult to grasp without the grace of a Guru. It posits that a scholar's attempt to comprehend these texts through their own efforts will fail, as the 'hidden truth does not come to hand' without the Guru's grace. According to this chapter, it is only for those who are humble, detached, and attached to the Guru's feet that the hidden meaning opens up automatically, as this path is otherwise 'difficult at every step'.