Why did Sai Baba keep a fire constantly burning in the Masjid, and what reminder did the resulting ash provide about our own existence?

Sai Baba kept the Dhuni constantly burning to produce the sacred ash, or Udi, which was central to his teachings. Chapter 33 explains the profound significance of this practice. The Udi served as a potent reminder about the nature of our existence. Baba intended for the ash to clearly show that all of the visible world is ultimately insubstantial, like ash. Specifically concerning our own existence, the teaching was that the body is like wood made of five elements, here only to experience its destiny. Once those experiences are exhausted, it too will become motionless and turn to ash, a state true for everyone. The Udi was given to help maintain this awareness constantly.