The ruling on taking a brokerage fee without the knowledge of the seller or the buyer

Question:
May Allah reward you. Honorable Shaykh, this man says in his question: Is it permissible for a man who is appointed as an agent to purchase camels or other items on behalf of a merchant to stipulate with the seller a specific amount in addition to the amount set by the agent, who is the buyer, without the buyer’s knowledge, given that he takes a fee in return for his services?

Answer:
It is not permissible for him to take anything other than the brokerage fee, other than the effort known as the effort; this is what is permissible for him, and it is what has become customary. If he stipulates this and the other party commits to it, then Muslims are bound by their conditions. However, he does not take anything except the effort, which is the brokerage fee, and he does not take it unless he seeks permission from the owner of the right or stipulates it upon him. Yes.