What specific Bhagavad Gita verse was the subject of the dialogue between Sai Baba and Nana, and what was Nana's initial explanation?

The dialogue between Sai Baba and Nana centered on a specific verse from the Bhagavad Gita. Chapter 39 identifies the original Sanskrit verse as: "Tadviddhi pranipatena, pariprashnena sevaya | Upadeksyanti te jnanam, jnaninastattvadarsinah". Nana, being an expert in Gita commentaries, provided the conventional explanation. With great humility, he explained that Lord Krishna's message to Arjuna was that one attains Knowledge by prostrating at the Guru's feet, serving the Guru, and through respectful questioning. He stated that by following this path, the Wise ones who have perceived the Truth will show the way to Knowledge.