Based on the story of Das Ganu and the Upanishads, what does Chapter 20 teach about the role of a Guru in attaining spiritual knowledge?

Chapter 20 presents a profound teaching on the necessity of a Guru for understanding complex spiritual texts. It argues that scriptures like the Upanishads, which hold the essence of the Vedas, are incredibly difficult to grasp through intellectual effort alone. The chapter explicitly states that a scholar who believes they can comprehend these texts by their own power will fail, as the 'hidden truth does not come to hand' without the Guru's grace. In contrast, for a humble and detached devotee attached to the Guru's feet, the path is made easy. As Chapter 20 reveals, the hidden meanings of Self-knowledge will open up automatically before their eyes, demonstrating that the Guru's grace is the indispensable key to true understanding.