The Bodhisatta was once an ascetic. There was a large festival in the city and both men and deities came to celebrate and have fun. While watching the goings on, a naga put his hand on the shoulder next to him, not noticing it was a garuda (these two types of deities are arch enemies) standing there. The naga fled in fear and the garuda gave chase.
Outside the city, the naga spotted the Bodhisatta bathing in the river and he took the form of a jewel and attached himself to the Bodhisatta’s clothes, which were laying on the bank. The garuda saw the naga hide there, but out of respect for the holy man, he did not attack. He did, however, tell the Bodhisatta what had happened and said he wanted to eat the naga. The Bodhisatta asked the garuda not to eat it and invited them both to come sit in his hut and listen to him preach about loving-kindness. They accepted and from then on out the pair lived in peace and harmony.
In the Lifetime of the Buddha
The naga and garuda were earlier births of two high-ranking royal military officers who hated each other and spoke rudely every time they met. Neither the king nor their friends and family could set them right. One day the Buddha divined that these two men were close to having a spiritual breakthrough, so the next morning he went out collecting alms at each of their houses. While sitting with them, the Buddha preached about loving-kindness and dharma so clearly they both became disciples. The two soldiers forgave each other and were harmonious from then on.
Later, when the Buddha heard some of his disciples discussing how he had humbled the two soldiers, he told them this story so they knew he had also reconciled the same two men in previous lives.