What's the story behind Sai Baba lighting lamps with water instead of oil?

Sai Baba had a great love for lighting lamps in the temple and mosque and would celebrate the festival of lights. As described in Chapter 5, his daily routine involved going to local shopkeepers to beg for oil. One day, the grocers conspired to refuse him, viewing his requests as a nuisance. When they all said no, Baba quietly returned to the mosque. He took a tin pot with a tiny bit of oil, poured water into it, drank it as an offering to the Supreme, and then filled the lamps with plain water. He then lit the water-soaked wicks, and miraculously, the lamps burned brightly all through the night, a testament to his divine power.