Sunan Ibn Majah, Chapter: The Chapters on Business Transactions

"The Messenger of Allah (saw) forbade selling what is in the wombs of cattle until they give birth, and selling what is in their udders unless it is measured out, and selling a slave who has fled, and selling spoils of war until it has been distributed, and selling Sadaqah until it has been received, and what a diver is going to bring up."