What is the story about Sai Baba climbing a ladder, and what was the lesson he taught through that incident?

Chapter 19 narrates a peculiar event where Sai Baba, despite being so physically weak that he needed two people to help him walk, suddenly called for a ladder. He had it placed against a house, climbed to the roof, crossed over to the neighboring roof of Radhakrishnabai's house, and then descended. This miraculous display of strength coincided with Radhakrishnabai suffering from a very high malarial fever, which he seemingly went to cure. Afterwards, he paid the man who brought the ladder two rupees. When questioned about the generous payment, Baba stated the lesson clearly: "One should not take the burden of anyone's labor for free, not even a bit." He taught that one must always compensate for any work received, establishing it as a rule for life.