Based on Chapter 20, what is the importance of a Guru for understanding spiritual scriptures like the Upanishads?

Chapter 20 powerfully argues that a Guru's grace is absolutely essential for understanding profound spiritual texts. It states that the Upanishads, which hold the essence of the Vedas, are 'very difficult to grasp' without the grace of God and Guru. The chapter explicitly refutes the idea that a scholar can comprehend these texts through their own effort, claiming that 'the hidden truth does not come to hand' and the path is difficult without a Guru. In contrast, for a devotee attached to the Guru's feet, the text says there is 'not even a bit of difficulty' and the hidden meaning opens up automatically.