There was once a rich and kindly old man who, reaching the end of his days, decided to leave his possessions to some honest and intelligent young man. Speaking of this decision, he told a good friend that he wanted to choose wisely. The friend advised him,"The next time you sell something, and are giving the customer their change, make sure you give them too much. the customer who returns the extra money to you, you will know that they are honest". The rich man thanked his friend for the advice, and thinking it a good idea, and easy to carry out, he decided to try it. What he did not know was this. One of those present during the conversation - a neighbour who pretended to be his friend, but was really very envious of the rich old man - hired the services of a wizard. He paid the wizard to cast a spell on the rich old man's coins. The spell would mean that anyone who saw coins touched by the old man, rather than seeing them as coins, would see them as that which the customer wanted most in the world. With this plan, the envious neighbour believed that no customer would return the old man's change, and, having no one to leave his money to, the old man would leave it all to the neighbour's young nephew. Indeed, everything went according to plan for the greedy neighbour, and not a single customer was able to return the enchanted coins. Some saw in these coins the biggest diamond or precious stone, others saw a work of art, some saw a relic, and some saw a miraculous healing potion. When the old man had almost given up trying to find an honest person, the greedy neighbour sent his nephew to the old man's business, taking great care to instruct the boy to return the old man's money. The nephew was determined to do so, but on receiving the enchanted coins he saw in them all the possessions and honours of his own uncle. Believing that what his uncle had told him was a trick, he left with his useless coins and his greed, to no end, since when his uncle learned of this betrayal, he made his nephew banish forever. The rich old man, sick and depressed, decided to call his servants before he died. He gave them some possessions so that they could live freely when he was no longer with them. Among these servants was a youth, who received some portion of this money by mistake. The youth, raised in the house of the wise and just old man, who he loved like a father, saw, in place of the money, a powerful medicine which would cure the old man, since this was truly what he most wanted in the world. On seeing this, the youth offered the money back to the old man, saying "Take this, sir, it's for you; it will make you feel better."And the return of that simple coin indeed acted like the most miraculous of cures. The old man leapt with joy at having finally found an honest person, and it filled him with joy to find that this honest person had always been in his very own house. And so, the young servant went on to manage, with great justice, generosity and honesty, all the old man's possessions and business concerns. And the old man went on to accompany and advise him like a son for many more years. 
The best way to encourage honesty is to create an environment of honesty and generosity, since he who wants nothing for himself is farthest from falling into greed and envy. 