The Bodhisatta was once a king and he ruled righteously by following the ten royal virtues. At that time, the people of the city used to make animal sacrifices to the gods, and when he was still just a prince, the Bodhisatta vowed to end this practice and devised a scheme to do so. He began joining the crowds who prayed to a tree fairy residing in a holy banyan tree outside the city, offering perfumes and flowers, sprinkling the tree with water, and walking around its trunk. Later, when he took the throne, he assembled his advisors and told them that when he was still the crown prince he had promised the tree fairy that if he became king he would make a great offering. He ordered them to go forth throughout the city and proclaim by beat of drum that the king had vowed to give the tree fairy the flesh and blood of one thousand subjects who break the commandments and live in sin. From this point forward, all evil-doers would be slayed and sacrificed. And as the king had predicted, not a single person was caught doing any bad things, including sacrificing animals.
In the Lifetime of the Buddha
One day some of the Buddha’s disciples sat around discussing how great the Buddha was: how he kept a simple life, was kind to all (even nagas and garudas), converted many people, and always lived for the benefit of the world. When the Buddha heard their discussion he told this story so they knew he had also acted in the interest of others in the past.
The king’s advisors were earlier births of the Buddha’s disciples.