What is the ruling on partnership in a company that deals with a factory which requests a commission, paid to it by reducing the percentage of raw materials supplied to another company without its knowledge, given that a large part of the profits from this partnership comes from this transaction?

It is not permissible for the partner and the manufacturer to take a commission from the company without its knowledge, or to cheat by reducing the percentage of raw material. You are not allowed to continue in a company that relies on deception and consuming wealth unlawfully. Your partner must avoid forbidden transactions or dissolve the partnership.

As for previous transactions, you both must either seek permission from the company owners or return the value of the difference between the agreed-upon and actual concentration percentage. Each of you bears his share of the profit. Whoever sells a defective product must return the amount of the defect to its owner, or give it as charity on his behalf if returning it is impossible. If a defect is found and the buyer is unaware of it, he has the option to either annul the contract or take the difference in price between them.