Sahih Muslim Book 010, Hadith Number 3691.
Chapter : It is forbidden to sell fresh dates against dry dates, except in case of al-Araya.
Sahl b. Abu Hathma reported Allah's Messenger (may peace be upon him) having forbidden Muzabana, i.e. exchange of fresh dates with dry dates. except in case of those to whom donations of some trees have been made. It is for them that concession has been given.