What miracle did Sai Baba perform when the shopkeepers refused to give him oil for the lamps?

When the grocers conspired to stop the 'nuisance' of giving free oil, they all refused Baba when he came to ask. As described in Chapter 5, Baba returned quietly to the mosque. He took his tin pot, which had a tiny bit of oil, poured water into it, and drank it as an offering to Brahman. He then filled the lamps with plain water, soaked the dry wicks, and lit them. To the amazement of the grocers, the lamps fueled by water burned brightly all through the night, demonstrating Baba's incredible power and causing the shopkeepers to repent for their actions.