Hazrat Abu Sa'id (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) forbade the sale and purchase of unborn animals in the womb until they are born, likewise forbade the sale and purchase of milk in the udders until it is milked and measured, the sale of a runaway slave, and the sale of spoils of war until they have been distributed, and the purchase of things that come as zakat until they have been taken into possession, and also forbade making a deal with a diver that he will dive into the sea and whatever he finds will be given to the buyer.