What is the ruling on selling an item to a person at a price higher than that at which it was purchased, if the buyer had requested to purchase it from the seller, and does the ruling differ if the buyer had authorized the seller to purchase it on his behalf?

The ruling differs depending on the nature of the transaction: If it is an agency, the agent is not permitted to profit from his principal except with the latter's knowledge, and he may agree with him on a known wage. However, if it is a trade, where one buys a commodity and sells it to the other for a profit, then there is no harm in that.