How did Sai Baba manage to light the lamps in the mosque when the shopkeepers refused to give him oil?

According to Chapter 5, when the local grocers and oil-merchants conspired to deny him oil, Sai Baba performed a significant miracle. He returned to the mosque with his tin pot, which had a very small amount of oil left. He poured water into that pot, drank it as an offering to Brahman, and then proceeded to fill the lamps with plain water. After soaking the dry wicks in this water, he lit them with a match. To the astonishment of the grocers who were watching, the lamps burned brightly throughout the entire night, demonstrating his divine power without a single drop of oil from them.