The Bodhisatta was once an untouchable. One time while out on a journey, he met a brahmin and they traveled together. When breakfast time came, the Bodhisatta stopped to eat and noticed the brahmin had not brought any food. The Bodhisatta offered him some, but the brahmin refused to eat the food of a low-caste person. When the Bodhisatta was done with his rice they continued walking, and the brahmin ate nothing all day.
When they stopped for dinner, the Bodhisatta did not offer the brahmin anything to eat, but he was so hungry he asked for some rice, and the Bodhisatta gladly shared. The brahmin tossed away the outer layer, which had been defiled by contact, and ate the rest. But as soon as he finished eating, he was overcome with remorse for having shamed his family this way and he vomited up the food, as well as some blood. Despondent, he ran off into the jungle where he died of grief.
In the Lifetime of the Buddha
There was a time when many of the Buddha’s disciples got alms in the twenty-one prohibited ways, such as doing work in exchange for food or sharing alms so each disciple did not need to go out seeking food every day. When the Buddha heard about this, he called the disciples together and told them to stop breaking these rules. Those who continued, he said, would be reborn in hell and return to earth as goblins or ghosts. Food received this way is like a piece of red-hot iron, deadly poison, or the leftovers of untouchables and would make misery for anyone who ate it, just like that which befell the brahmin who broke his own rule. Then he told them this story to explain.
The Buddha did not identify any earlier births other than his own.