Reb Yaakov Abudram and Reb Naftali Azaryah were goldsmiths in Paris, France, and they often did business together. One year, they fasted on erev Rosh Hashanah, and they davened that Hashem should reveal to them how much money they would earn the following year.
They both had a dream that night. One dreamt that he would earn 200 gold coins, and the other dreamt that he would earn 150 gold coins.
They went to Reb Yechiel of Paris zt'l (one of the baalei haTosfos) and told him about their dreams. Reb Yechiel told them that throughout the year, they should write down exactly how much money they earn and return to show him their papers at the end of the year.
Sometime in the middle of the year, there was a din Torah between these two smiths. They invested in a certain business together, there were profits, and they disagreed on what they had initially agreed on, regarding how to divide the profits. Reb Yaakov Abudram said they invested the same amount of money and agreed to split the profits 50/50. Reb Naftali Azaryah claimed that he put down 2/3rds of the investment, and they agreed that he would receive 2/3rds of the gain. Ultimately, the debate was over 10 gold coins. If Reb Naftali Azaryah got his way, he would receive ten coins more.
Reb Yechiel ruled that since the money was already in Reb Yaakov's possession, Reb Naftali didn’t have a right to the ten gold coins. This is based on the rule מחבירו המוציא הראיה עליו; you can't take money away from another person without proof. "However," Reb Yechiel added, "Reb Yaakov has to swear that the money is his." Reb Yaakov didn't want to swear, so he paid the ten gold coins to Reb Naftali.
On the last night of the year, Reb Naftali and Reb Yaakov came to Reb Yechiel of Paris to show him their ledgers of how much money they had earned that year. Reb Yaakov earned 190 gold coins (ten less than his dream), and Reb Naftali earned 160 (ten more than his dream).
Reb Yechiel said to Reb Naftali, "Do you remember the dream you had at the beginning of the year? It seems you didn't have a right to the ten gold coins you received from Reb Yaakov!"
Reb Naftali countered, "It was just a dream. It doesn't have any halachic significance." Reb Yechiel explained, "I didn't say that according to halachah you must give back the ten coins. It was just advice, based on how things appear." Reb Naftali decided that since it wasn’t halachah, just a recommendation, he wouldn’t give back the ten gold coins.
The following day, on erev Rosh Hashanah, Reb Naftali and Reb Yaakov went to their stores to do business until midday. Reb Yaakov earned ten gold coins that morning. (This isn't surprising. He was destined to earn 200 gold coins that year). But no one came into Reb Naftali's store. At midday, Reb Naftali Azaryas closed his store. As he was walking home, he passed a storefront where glass items were sold. He tripped and fell on an expensive piece. The goyishe owner of the store hit him and brought him to the judge, who obligated him to pay ten gold coins for the damages.
Reb Naftali's wife didn't know where her husband was, and why he wasn't coming home. When he finally arrived, it was Rosh Hashanah, and he said, "I want to go to Reb Yechiel." In the home of the holy baal haTosfos, Reb Yechiel of Paris, Reb Naftali asked him for forgiveness for not listening to him. Reb Yechiel told him, "You don't have to ask me mechilah. You didn't do anything to me. You have to ask mechilah from Reb Yaakov."
The next day, before tekiyas shofar, Reb Yechiel told this story to his congregation, to teach them to be cautious not to steal the money of others.
