Tell me about the devotee who forgot his vow and how Sai Baba helped him.

In Chapter 36, Sai Baba explains the case of a man from whom he insisted on taking fifteen rupees as Dakshina. Baba told Shama that this man was initially poor and, upon getting a job, had made a vow to give his first month's salary of fifteen rupees to God. However, he forgot this promise. As his salary grew from fifteen to thirty, sixty, one hundred, and eventually seven hundred rupees, his forgetfulness grew stronger. Baba explained that the man arrived at Shirdi by the power of his past good deeds, and it was then that Baba, under the pretext of asking for Dakshina, reminded him of his obligation by asking for the original fifteen rupees. In doing so, Baba wasn't taking money for himself but was helping the devotee clear his long-standing spiritual debt.