The story goes about that three immortals reincarnated themselves into three poor old people and begged food from a fox, a monkey and a rabbit. The fox and monkey both gave food to the immortals. However, the rabbit did not have any food. It then said to the immortals: “you can eat me” and jumped into the fire.
The immortals were so moved by the rabbit and sent it to the moon to become an immortal jade rabbit. Ever since, the jade rabbit stayed in the Moon Palace to accompany Chang E and pounded immortal medicine for those living in the heaven.
From: Travel China Guide