Can you tell me the story of how Sai Baba lit lamps with water? Why did he even need to do that?

Sai Baba had a great love for lighting lamps in the mosque and temple for the festival of lights. As described in Chapter 5, he would personally go to the local grocers and oil-merchants to beg for oil each day. However, the grocers grew tired of this and conspired to deny him. When Baba came for oil, they all refused. In response, Baba returned to the mosque, took a tin pot with a minuscule amount of oil, added water to it, and drank it as an offering. He then filled the lamps with plain water and lit them. Miraculously, the lamps burned brightly all night long, demonstrating his divine power to the astonished and repentant shopkeepers.