What is the origin and daily practice associated with Sai Baba's Udi as described in Chapter 33 of the Sai Satcharitra?

According to Chapter 33 of the Shri Sai Satcharita, the Udi is the sacred ash originating from the Dhuni, or sacred fire, that Sai Baba kept perpetually burning in the Masjid. Baba would purchase bundles of firewood, offer the dry logs to the fire, and the resulting ash was the Udi. The chapter details that distributing this Udi was a consistent daily practice. Baba would give it to devotees in the mornings, afternoons, and evenings, ensuring no one was sent away empty-handed. This routine also included the specific practice of giving Udi to devotees as a sign of permission when they were set to depart from Shirdi for their homes.