Is it permissible for a buyer, who was authorized by his friend to purchase 5 cans of tomatoes at a known price (18 dinars per can), to buy 10 cans at the wholesale price (16 dinars per can) without his principal's knowledge, then take 5 cans for himself at 14 dinars per can, and give his principal the 5 cans he requested at 18 dinars per can, knowing that the principal is aware that the wholesale price is lower than the retail price?

The questioner acts as an agent for his friend in purchasing. If he gave him 90 dinars, then he is entitled to a portion of the goods equivalent to this amount, according to the actual price at which the questioner purchased them, or the excess money should be returned to him.

Therefore, either the questioner informs his friend about what happened and seeks his forgiveness, or he returns 10 dinars to him, or he gives him a portion of the goods equivalent to his money, but this is difficult because it would necessitate dividing one of the packages between them.