From: Anecdotes of the Pious Ones, # 33, V. 1

Imam Sadiq's (as) family and dependents had grown in number. Imam thought of starting some bussines, so that the expenses of the family could be provided for. He gave one thousand Dinars to his servant named Musadif, and told him: "Take this money and go to Egypt for trade."

Musadif purchased products that were marketable in Egypt, and left with a caravan.

As they arrived in Egypt, another caravan was leaving Egypt. It came to their attention that the goods, that Musadif had brought, had a competitive market in Egypt, and has become rare. Whoever had those goods, were very happy for thier good luck. As the good happened to be a basic neccisity of life, people had to purchase it for any price.

The merchants agreed that they will sell it only double the price. Thus they went to the market place, and sold the item double the purchase price as they had agreed.

Musadif returned with two thousand Dinars. Happily he went to the Imam (as) and put the two bags of money infront of him.

Imam (as) asked: "What are these?"

He said: "One of the bags is the initial capital. The next is the interest."

Imam (as): The interest is a large sum. Tell me how you earned all this?"

"We were informed that the goods we had along was rare in Egypt. So we decided and swore to sell it double its value."

"Subhan Allah! You did such a thing! You swore to form a black market among the Muslims. You swore not to sell it but double the value! I do not want such trade. I don't want such profit.

Then Imam picked one of the bags and said: "This is my capital." He didn't touch the other, and said: "I have nothing to do with this."

Then he said: "Fighting with sword is easier than earning Hallal sustenance." [1]

[1] Bihar al Anwar, V. 11, p 121