Can you recount the puzzling incident involving two gentlemen from Goa and their offerings to Sai Baba?

Certainly. Chapter 36 details an event where two gentlemen from Goa came for Sai Baba's darshan. Both men approached Baba and surrendered at his feet. In a curious display, Sai asked for a Dakshina of fifteen rupees from only one of the men, which he accepted when given. However, when the second gentleman, unprompted, offered thirty-five rupees on his own accord, Sai Baba immediately rejected it. This seeming partiality surprised everyone present, including Madhavrao (Shama), who felt compelled to ask Sai for an explanation of his actions.