The Jataka, Vol. II, tr. by W.H.D. Rouse, , at sacred-texts.com
"Who could believe the story," etc.--This story the Master told at Jetavana about a dishonest merchant. The circumstances have been told above.
Once upon a time, when Brahmadatta was king of Benares, the Bodhisatta was born in the family of a landed proprietor.
When he grew up, he became a wealthy man. He had a young brother. Afterwards their father died. They determined to arrange some business of their father's. This took them to a village, where they were paid a thousand pieces of money. On their way back, as they waited on a river-bank for the boat, they ate a meal out of a leaf-pottle. The Bodhisatta threw what he left into the Ganges for the fishes, giving the merit to the river-spirit. The spirit accepted this with gratification, which increased her divine power, and on thinking over this increase of her power, became aware what had happened. The Bodhisatta  laid his upper garment upon the sand, and there he lay down and went to sleep.
Now the young brother was of a rather thievish nature. He wanted to filch the money from the Bodhisatta and keep it himself; so he packed a parcel of gravel to look like the parcel of money, and put them both away.
When they had got aboard, and were come to mid-river, the younger stumbled against the side of the boat, and dropt overboard the parcel of gravel, as he thought, but really the money.
"Brother, the money's overboard!" he cried. "What's to be done?"
"What can we do? What's gone is gone. Never mind about it," replied the other.
But the river-spirit thought how pleased she had been with the merit she had received, and how her divine power had been increased, and resolved to take care of his property. So by her power she made a big-mouthed fish swallow the parcel, and took care of it herself:
When the thief got home, he chuckled over the trick he had served his brother, and undid the remaining parcel. There was nothing but gravel to be seen! His heart dried up; he fell on his bed, and clutched the bedstead.
Now some fishermen just then cast their nets for a draught. By power of the river-spirit, this fish fell into the net. The fishers took it to town to sell. People asked what the price was.
"A thousand pieces and seven annas," said the fishermen.
Everybody made fun of them. "We have seen a fish offered for a thousand pieces!" they laughed.
The fishers brought their fish to the Bodhisatta's door, and asked him to buy it.
"What's the price?" he asked.
"You may have it for seven annas," they said.
"What did you ask other people for it?"
"From other people we asked a thousand rupees and seven alms; but you may have it for seven arenas," they said.
He paid seven arenas for it, and sent it to his wife. She cut it open, and there was the parcel of money!  She called the Bodhisatta. He gave a look, and recognising his mark, knew it for his own. Thought he, "These fishers asked other people the price of a thousand rupees and seven annas, but because the thousand rupees were mine, they let me have it for seven annas only! If a man does not understand the meaning of this, nothing will ever make him believe:" and then he repeated the first stanza:--
When he had said this, he wondered how it was that he had recovered his money. At the moment the river-spirit hovered invisibly in the air, and declared--
"I am the Spirit of the Ganges. You gave the remains of your meal to the fishes, and let me have the merit. Therefore I have taken care of your property;" and she repeated a stanza:--
 Then the spirit told about the mean trick which the younger brother had played. Then she added, "There he lies, with his heart dried up within him. There is no prosperity for the cheat. But I have brought you your own, and I warn you not to lose it. Don't give it to your young thief of a brother, but keep it all yourself." Then she repeated the third stanza:--
[paragraph continues] Thus spoke the spirit, not wishing that the treacherous villain should receive the money. But the Bodhisatta said, "That is impossible," and all the same sent the brother five hundred.
After this discourse, the Master declared the Truths:--at the conclusion of which the merchant entered upon the fruition of the first path:--and identified the Birth:--"At that time the younger brother was the dishonest merchant, but the elder was I myself."
288:1 Folk-lore Journal, iii. 364.