Sheikh Sa`ûd al-Funaysân, former professor at al-Imâm University
If the owner of the steel has delegated to his sales agent to secure for him a certain fixed price and then authorized him to take any excess that he makes for himself, then the extra money is perfectly lawful for the agent as well as for the brokers with whom that agent does business.
Such conditions in business are lawful, for the Prophet (peace be upon him) said: “Muslims are to have their conditions upheld, except for a condition that permits something unlawful or prohibits something lawful.” [Sunan al-Tirmidhî (1352) and Sunan Ibn Mâjah (2353)]
On the other hand, if the owner of the steel has not permitted his agent to take for himself that which is in excess of a pre-agreed price, then the agent’s doing so is unlawful. Consequently, it will be unlawful for the brokers to share in that money. In doing so, the brokers are, in fact, colluding with the agent in permitting something that is unlawful, because they are consuming the owner’s rightful wealth unlawfully.
Anything that has its basis in something false and unlawful will be equally false and unlawful.
Allah says: “Do not eat up your property among yourselves in falsehood, nor use it as bait for judges in order that you consume some of the wealth of others sinfully while you know better.” [Sûrah al-Baqarah: 188]
The Prophet (peace be upon him) said: “Flesh that is nurtured on unlawful sustenance is most suited for the Hellfire.” [Sunan al-Tirmidhî (614)]
The brokers, by bringing customers to the agent and partaking of this money are helping the agent in sin and transgression.
Allah says: “Help one another in righteousness and piety, and do not help one another in sin and transgression. And fear Allah. Indeed, Allah is severe in punishment.” [Sûrah al-Mâ’idah: 2]
The Prophet (peace be upon him) said: “Leave off that which causes you doubt for that which does not cause you to doubt.” [Sunan al-Tirmidhî (2518) and Sunan al-Nasâ’î (5711)]
The Prophet (peace be upon him) also said: “Sin is whatever disquiets the heart that you detest people coming to know about.” [Sahîh Muslim (2553)]
Honestly, I do not think that the business you describe is anything but what the Prophet (peace be upon him) has described as sin.
And Allah knows best.
Source: Islam Today