Why did Sai Baba accept Dakshina from one man from Goa but reject a larger amount from his friend? What was his initial explanation?

In Chapter 36, the apparent partiality of Sai Baba is questioned by his devotee Shama. When two friends from Goa visited, Baba asked for and received fifteen rupees from one but rejected a voluntary offering of thirty-five rupees from the other. When Shama asked about this, Baba began his explanation by revealing a profound spiritual principle. He said, "Shama, you don't know; I don't take anything from anyone. Mother Masjid demands what is owed, and the giver becomes free from debt." This indicates the transaction was not about monetary value but was related to a pre-existing debt from a past life, which Baba was helping to settle.