Why did Sai Baba make the woman who wanted to fast for three days eat puranpolis instead, and what was the lesson?

In an incident described in Chapter 32, a woman arrived with the firm resolve to have Baba's darshan and fast for three days. Sai Baba intervened and broke her resolve by having her prepare and then eat puranpolis to her heart's content. The deeper meaning behind this, as explained in Chapter 32, was to teach her a lesson she would never forget about the nature of true spiritual welfare. Baba demonstrated that while fasting has its virtues, the act of serving others and "wearing out the body for others' sake" is a blessed act that represents supreme welfare, placing selfless service above personal austerity.