How did Sai Baba prove his divine nature to the villagers of Shirdi when they initially thought he was mad?

According to Chapter 0, the villagers of Shirdi initially considered Maharaj to be a mad Fakir. Their delusion was removed through a miraculous event involving lamps. Maharaj was fond of lighting many lamps in the Masjid and temples, but one day the local grocers refused to give him oil. Unfazed, Maharaj filled the lamps with water instead of oil and lit them as usual. The villagers were amazed when the lamps lit just like normal and continued to burn all night. This event made them realize his true worth, causing them to surrender to him and apologize for their prior behavior.