The Jataka, Vol. II, tr. by W.H.D. Rouse, , at sacred-texts.com
 "The barb is in your back," etc.--This story the Master told while dwelling in Jetavana, about a backsliding brother.
He was brought into the Hall of Truth, and asked if he were really backsliding; to which he replied yes. When asked why, he replied "Because of the quality of desire." The Master said, "Desire is like two-barbed arrows for getting lodgement in the heart; once there, they kill, as the barbed arrows killed the crocodile." Then he told them an old-world tale.
Once upon a time, the Bodhisatta was king of Benares, and a good king he was. One day he entered his park, and came to the side of a lake. And those who were clever with dance and song began to dance and to sing. The fish and tortoises, eager to hear the sound of song, flocked together and went along beside the king. And the king, seeing a mass of fish as long as a palm trunk, asked his courtiers,
"Now why do these fish follow me?"
Said the courtiers, "They are coming to offer their services to their lord."
The king was pleased at this saying, that they were come to serve him, and ordered rice to be given to them regularly. At the time of feeding some of the fish came, and some did not; and rice was wasted. They told the king of it. "Henceforward," said the king, "at the time for
the giving of rice let a drum be sounded; and at the sound of the drum, when the fish flock together, give the food to them." From thenceforth the feeder caused a drum to sound, and when they flocked together gave rice to the fish. As they were gathered thus, eating the food, came a crocodile and ate some of the fish. The feeder told the king. The king listened. "When the crocodile is eating the fish," said he, "pierce him with a harpoon, and capture him." 
"Good," the man said. And he went aboard a boat, and so soon as the crocodile was come to eat the fish, he pierced him with a harpoon. It went into his back. Mad with pain, the crocodile went off with the harpoon. Perceiving that he was wounded, the feeder spake to him by this stanza:
When the crocodile got to his own place, he died.
To explain this matter, the Master having become perfectly enlightened spake the second verse as follows:
 When this discourse was ended, the Master declared the Truths and identified the Birth:--at the conclusion of the Truths, the backsliding Brother reached the Fruit of the First Path:--"In those days I was the king of Benares."