Can you summarize the main events and teachings detailed in the 20th chapter of Sai Satcharitra?

Chapter 20 of the Sai Satcharitra covers several key events and teachings. It begins by describing the loving scene after the noon Aarti in Shirdi, where Sai Baba distributes Udi to his devotees. The chapter then transitions to the story of Das Ganu, who was writing a commentary on the Ishavasya Upanishad but became stuck, unable to comprehend its deeper meaning. When he approached Baba, he was told a maidservant would resolve his doubt. This narrative serves to illustrate a core teaching of the chapter: the absolute necessity of a Guru's grace to understand profound spiritual texts like the Upanishads.