Explain the connection between the Dhuni, the firewood, and the ultimate spiritual lesson Sai Baba imparted with the Udi, based on Chapter 33.

Chapter 33 of the Sai Satcharitra masterfully links the physical process of maintaining the Dhuni to a profound spiritual teaching. The chapter describes the process: Baba would buy firewood, offer the logs into the sacred Dhuni, and collect the resulting ash, or Udi. This cycle was a living parable. The firewood symbolized the transient nature of the physical body and the entire material universe. Offering it to the fire represented the eventual dissolution of all forms. The final product, the Udi, was the ultimate spiritual lesson in tangible form. It served as a constant reminder of impermanence and the truth that everything visible is illusory (Maya) and will become ash. Through this, Baba taught that only Brahman is the eternal, unchanging reality, a lesson devotees were to internalize by accepting the sacred ash.