"Say, who is there to forbid the beauty which Allah has brought forth for His creatures, and the good things from among the means of sustenance. Say, they are for those who believe (in Allah) in this worldly life, to be theirs alone in the Hereafter on the Day of Resurrection. Say, the only things my Lord forbids are the shameful deeds, be they open or secret, the sin, unjustified envy, the ascribing of divinity to aught beside Allah, and the attributing unto Allah of aught of which you have no knowledge.”
So everyone is free to conduct any business he likes outside the harmful circle he has been warned not to indulge in. If he does not listen to this warning, he will be in trouble. Every good quality as precondition to a successful business is encouraged by Islam.
The Prophet Sallallahu Alayhi Wasallam himself was a businessman before he was appointed as a Prophet. His ability to run business prudently, by his fairness and truthful conduct in dealing with people had won him the heart of his employer, Khadija RA who later offered him marriage. He advocated Muslims to follow the spirit of Prophet Daud (David) of hard work, earned his living from his own labour. He also said that faith of a Muslim is not complete if he is not good in his profession. He said: ‘If you leave matters to those who are not professional] you are waiting for the disaster'.
If he works in the production line, his products must be compatible with products of other companies or factories. In order to be marketable, it must suit the taste of buyers and their standards of living. In this regard, Islam teaches not to cheat in offering the product to the market. It must be shown as it is without any publicity it does not deserve. In the life time of the Prophet Sallallahu Alayhi Wasallam, he found many cases in market places where the merchants tried to cheat the customers. The Prophet said to them: "Whoever cheated are not from amongst us (Muslims)".
Islam laid many regulations in the field of economy such as trade, leasing, business transactions, contracts and others to prevent unfair dealing within the community and in the world of business at large. What is also prevented by Islam is a monopoly and exploitation 'by one man or one group at the expense of the others.