Can you summarize the key events and teachings described in Chapter 20 of the Sai Satcharitra?

Chapter 20 of the Sai Satcharitra primarily covers two interconnected themes. First, it paints a vivid picture of the scene in Shirdi after the noon Aarti, where Sai Baba lovingly distributes Udi to his devotees, applying it to their foreheads and urging them to go have their meals. As this chapter explains, this act demonstrates his immense mercy. The narrative then introduces the story of Das Ganu, who was writing a Marathi commentary on the Ishavasya Upanishad. He encountered a profound doubt he couldn't resolve and sought Baba's help, setting the stage for a unique teaching about the necessity of a Guru's grace.