The Bodhisatta was once a wealthy merchant. A merchant from the border region that he knew only through correspondence sent a large caravan to trade merchandise with the Bodhisatta. While they were in his city, the Bodhisatta lodged the men and gave them some spending money. Soon after, the Bodhisatta sent his own large caravan to the border merchant, but he did not provide food, lodging, or even simple courtesy to the Bodhisatta’s men.
When the border merchant sent a second caravan to trade with the Bodhisatta, his men had them set up camp outside the city and said provisions would be brought later, but instead the men came in the night and looted the caravan, taking everything of value, including their wagon wheels. Later, when the Bodhisatta learned what his men had done, he told the crowd around him that ungrateful people get what they deserve.
In the Lifetime of the Buddha
Anathapindika, a wealthy supporter of the Buddha known for his extreme generosity, told the Buddha that recently he had treated some traveling merchants very generously, but his men had not been shown the same courtesy in return, so his men robbed the merchants when they came back a second time.
The Buddha told Anathapindika this story so he knew that he himself once had the exact same interactions with an earlier birth of this border merchant.