The Jataka, Vol. II, tr. by W.H.D. Rouse, , at sacred-texts.com
"Well planned indeed!" etc.-- This story the Master told while staying in Jetavana, about a dishonest trader.
There were two traders of Sāvatthi, one pious and the other a cheat. These two joined partnership, and loaded five hundred waggons full of wares, journeying from east to west for trade; and returned to Sāvatthi with large profits.
The pious trader suggested to his partner that they should divide their stock. The rogue thought to himself, "This fellow has been roughing it for ever so long with bad food and lodging. Now he's at home again, he'll eat all sorts of dainties and die of a surfeit. Then I shall have all the stock for myself." What he said was, "Neither the stars nor the day are favourable; to-morrow or the next day we'll see about it;" so he kept putting it oft: However, the pious trader pressed him, and the division was made. Then he went with scents and garlands to visit the Master; and after a respectful obeisance, he sat on one side. The Master asked when he had returned. "Just a fortnight ago, Sir," said he. "Then why have you delayed to visit the Buddha?" The trader explained. Then the Master said, "It is not only now that your partner is a rogue; he was just the same before;" and at his request told him an old-world tale.
Once upon a time, while Brahmadatta was king of Benares, the Bodhisatta came into this world as the son of one in the king's court. When he grew up he was made a Lord Justice.
At that time, two traders, one from a village and one of the town, were friends together. The villager deposited with the townsman five hundred ploughshares. The other sold these, and kept the price, and in the place where they were he scattered mouse clung. By and by came the villager, and asked for his ploughshare 1. "The mice have eaten them up 2!" said the cheat, and pointed out the mouse clung to him.
"Well, well, so be it," replied the other: "what can be done with things which the mice have eaten?
Now at the time of bathing he took the other trader's son, and set him in a friend's house, in an inner chamber, bidding them not suffer him to go out any whither.  And having washed himself he went to his friend's house.
"Where is my son?" asked the cheat.
"Dear friend," he replied, "I took him with me and left him on the river side; and when I was gone down into the water, there came a hawk, and seized your son in his extended claws, and flew up into the air. I beat the water, shouted, struggled--but could not make him let go."
"Lies!" cried the rogue. "No hawk could carry off a boy"
"Let be, dear friend: if things happen that should not, how can I help it? Your son has been carried off by a hawk, as I say."
The other reviled him. "Ah, you scoundrel! you murderer! Now I will go to the judge, and have you dragged before him!" And he departed. The villager said, "As you please," and went to the court of justice. The rogue addressed the Bodhisatta thus
"My lord, this fellow took my son with him to bathe, and when I asked where he was, he answered, that a hawk had carried him off. Judge my cause!"
"Tell the truth," said the Bodhisatta, asking the other.
"Indeed, my lord," he answered, "I took him with me, and a falcon has carried him off."
"But where in the world are there hawks which carry off boys?"
"My lord," he answered, "I have a question to ask you. If hawks cannot carry off boys into the air, can mice eat iron ploughshares?"
"What do you mean by that?"
"My lord, I deposited in this man's house five hundred ploughshares. The man told me that the mice had devoured them, and showed me the droppings of the mice that had done it. My lord, if mice eat ploughshares, then hawks carry off boys: but if mice cannot do this, neither will hawks carry the boy off. This man says the mice ate my ploughshares. Give sentence whether they are eaten or no.  Judge my cause!"
"He must have meant," thought the Bodhisatta, "to fight the trickster with his own weapons.--Well devised!" said he, and then he uttered these two verses:--
"A rogue out-rogued with tit for tat!
Give back the plough, and after that
Perhaps the man who lost the plough
May give your son back to you now!" 1
 Thus he that had lost his son received him again, and he received his ploughshare that had lost it; and afterwards both passed away to fare according to their deeds.
When this discourse was ended, the Master identified the Birth:--"The cheat in both cases was the same, and so was the clever man; I myself was the Lord Chief Justice."
127:1 Here, in the last sentence but one, and in the verses the singular phālaṁ is used. It is possible this may be a collective, but more likely that it harks back to a simpler and older version, where only one is spoken of. Readers cannot fail to have marked the fondness of the Jātaka editor for round numbers, especially five hundred.
127:2 Things gnawed by mice or rats were unlucky; cp. vol. 1. p. 372 (Pāli), Tevijja-Sutta Mahāsīlaṁ i (trans. in S. B. E., Buddhist Suttas, p. 196). The man here goes further than he need; if the mice had but nibbled the ploughshares perhaps he might throw them away.--We may also have a reference to an old proverb, found both in Greek and Latin: "where mice eat iron" meant "nowhere." Herondas 3. 76 οὑδ᾽ ὅκου χώρης οἱ μῦς ὁμοίως τὸν σίδηρον τρώγουσιν. Seneca, Apocolocyntosis chap. 7 (to Claudius in heaven) venisti huc ubi mures ferrum rodunt.
129:1 A like repartee is found in North Ind. N. and O. iii. 214 (The Judgement of the Jackal); Swynnerton, Ind. Nights Entertainments, p. 142 (The Traveller and the Oilman); and a story of an oilman in Stumme's Tunische Märchen, vol. ii.