The texts mention an "exchange" between Sai Baba and Tatya Patil. What does this refer to and what was the outcome?

The "exchange" refers to the belief that Sai Baba sacrificed his own life to save Tatya Patil. According to Chapter 42, Baba had predicted that Tatya would pass away on Vijayadashami of Shaka 1840. As that day arrived, Tatya was critically ill, and his relatives were grieving. Simultaneously, Baba's own health was rapidly declining. In a miraculous turn of events, Tatya's crisis passed and he recovered, while Baba himself entered Mahasamadhi at that very time. The people of Shirdi interpreted this as Baba giving "the exchange of his own body for Tatya's death." This act, as Chapter 42 explains, was a profound mystery that was not understood until after it happened, highlighting Baba's unfathomable compassion and his control over his own departure.