I read that one should not go empty-handed to a Guru. How is this principle demonstrated in the story of the grapes?

The principle of not approaching a Guru, God, or priest empty-handed is explicitly mentioned and demonstrated in Chapter 35. The text states, "It is not good to go empty-handed to the door of God, a priest, or a Guru." Adhering to this, a devotee named Kaka bought two seers of grapes to offer to Sai Baba upon arriving in Shirdi. It was these very grapes, offered with devotion, that became the medium for the miracle that transformed the skeptical Boss Dharamsee. Baba used Kaka's offering to distribute prasad and perform the miracle of turning the seeded grapes into seedless ones for Dharamsee, thereby dissolving his ego and planting the seed of faith. This shows how a devotee's offering can become a tool in the Guru's hands for the spiritual benefit of others.