Why did the shopkeepers in Shirdi refuse to give Sai Baba oil for his lamps, and what was the consequence of their actions?

According to the account in Chapter 5, the grocers and oil-merchants had been providing Sai Baba with free oil daily for the lamps in the temple and mosque. They grew tired of this and, with a 'wicked idea,' conspired to refuse him. As a consequence of their dishonesty, they witnessed a divine miracle. After they said 'no,' Baba lit the lamps using only water, and they burned all night. Seeing this, the grocers were astonished and filled with repentance. They realized they had sinned by lying and causing Baba trouble, and they began to tremble, feeling unworthy of his grace.