Is it permissible for Ahmed to take the price of the commodity from his friend Mahmoud, if the shop owner forgave its price or reduced its value?

Ahmad is acting as an agent for his friend in a purchase, and any discount or gift resulting from this purchase belongs to the friend, the buyer. The gift resulting from the sale is considered an increase in the price and is attached to the contract, as narrated from Imam Ahmad regarding the ruling on a gift from the buyer to the seller of a garment on behalf of an agent.