The Bodhisatta was once a buffalo. One day a rude monkey came down from its tree to play on the Bodhisatta – he hung from his horn, swung on his tail, and defecated on his back. Being full of patience and mercy, the Bodhisatta ignored the monkey’s misconduct. And so the monkey came and did it again and again, day after day.
A tree fairy who resided in the monkey’s tree asked the Bodhisatta why he allowed such behavior and didn’t trample or gore the monkey. He answered that his destiny required moral behavior, but he was sure that someday the monkey would do it to a different buffalo and get the fate he deserved leaving the Bodhisatta guiltlessly free of this irritation. And as the Bodhisatta predicted, when a different buffalo stood below the monkey’s tree he climbed down to make mischief just as he always did. But this other buffalo shook the monkey off his back, drove a horn through his heart, and trampled him into mincemeat.
In the Lifetime of the Buddha
One day a family’s pet monkey climbed onto an elephant’s back and defecated. The elephant was virtuous and patient and did nothing in response. But when the monkey returned to the stable another day there was a different elephant in it. When it suffered similar mischief, this elephant picked up the monkey in its trunk and smashed it to the ground then trod all over it.
When the Buddha heard some of his disciples discussing how the monkey had died, he told them this story so they knew this very same monkey had behaved and suffered similarly in an earlier birth. The bad buffalo was an earlier birth of the bad elephant.