The massacre of the Sakya clansmen
Before the advent of Sakyamuni Buddha, there was near Kapila town a village inhabited by fishermen, and in it was a big pond. It happened that because of a great drought, the pond ran dry and all the fish were caught and eaten by the villagers. The last fish taken was a big one and before it was killed, a boy who never ate fish, played with it and thrice knocked its head.
Later, after Sakyamuni Buddha's appearance in this world, King Prasenajit who believed in the Buddha-dharma, married a Sakya girl who then gave birth to a prince called Crsytal. When he was young, Crystal had his schooling in Kapila which was then inhabited by the Sakya clansmen. One day while playing, the boy ascended to the Buddha's seat and was reprimanded by others who dragged him down. The boy cherished a grudge against the men and when he became king, he led his soldiers to attack Kapila, killing all its inhabitants.
At the same time, the Buddha suffered from a headache which lasted three days. When His disciples asked Him to rescue the poor inhabitants, the Buddha replied that a fixed Karma could not be changed. By means of his miraculous powers, Maudgalyayana rescued five hundred Sakya clansmen and thought he could give them refuge in his own bowl which was raised up in the air. When the bowl was brought down, all the men had been turned into blood.
When asked by His chief disciples, the Buddha related the story of the villagers who in days gone by had killed all the fish in their pond; King Crystal had been the big fish and his soldiers the other fish in the pond; the inhabitants of Kapila who were now killed had been those who ate the fish; and the Buddha Himself had been the boy who thrice knocked the head of the big fish. Karma was now causing Him to suffer from a headache for three days in retribution for his previous act. Since there could be no escape from the effects of a fixed Karma, the five hundred Sakya clansmen, although rescued by Maudgalyayana, shared the same fate. Later, King Crystal was reborn in a hell.
As cause produces effect which in turn becomes a new cause the retribution is inexhaustible. The law of causality is really very dreadful.