The Bodhisatta was once a tree fairy. A lion and a tiger lived together in a cave and they let a jackal eat their leftover meat. The jackal had never eaten lion or tiger meat and wanted very much to do so. He knew if he got the two friends arguing they would kill each other and he would get his special meal.
So he told the lion the tiger spoke poorly of him, saying the lion was not even one sixteenth as beautiful or strong as he was. The lion sent the jackal away, saying the tiger would never say such things. Then the jackal told the tiger the same lie about the lion. The tiger went and asked his friend if it was true, and the lion denied it. The tiger apologized for doubting him and the lion forgave him. The two remained close friends and the jackal fled. The Bodhisatta saw it all happen.
In the Lifetime of the Buddha
The lion and tiger were earlier births of Sariputta and Moggallana, two of the Buddha’s top disciples. They spent a rainy season living in the wilderness and a beggar (the jackal was an earlier birth of him) lived nearby, assisting them in exchange for leftover food. Because the two elders lived so harmoniously, the beggar decided to try and make them quarrel. He told Sariputta that Moggallana spoke poorly of him, saying he’s lower in both lineage and spiritual attainments. Sariputta knew it was a lie. Then the beggar told Moggallana the same story, and he also rejected it. The two elders sent the beggar away.
When they returned to the Buddha’s monastery, Sariputta that Moggallana told him about their experience with the beggar and the Buddha told them this story so they knew he had done the same thing to them in the past.