It was on Ganesha Chaturthi. Ganesha was riding on his little rat and suddenly a snake crossed his path. The rat was terrified and ran off in fright due to which Ganesha fell down in a thorny bush.
The Moon was looking at this from the sky. The Moon laughed loudly at the funny sight of Ganesha’s falling down, It annoyed Ganesha so much so that he decided to punish the Moon. Angrily he broke one of his tusks and threw it at the Moon.
As it struck the Moon, Moon lost the brightness. Then the moon went off. The world became dark. People were scared and they screamed and wept.
All the Gods in heaven were worried by this confusion. They prayed to Ganesha,” please give back the Moon the brightness, “The Moon also repented. The Moon fell at Ganesh’s feet and prayed to be forgiven.
Ganesha relented but he wanted to teach Moon a lesson. So he said, “the first fifteen days of every month, you will get bigger and then the next fifteen days, you will become smaller and smaller. At the end of the month, you will look like my tusk. And on the day of Ganesh Chaturthi, the person who looks at the Moon will have an allegation of theft on him.