Sahih Muslim Book 10, Hadith Number 3692.

Chapter : It is forbidden to sell fresh dates against dry dates, except in case of al-Araya.

Abu Huraira (Allah be pleased with him) reported Allah’s Messenger (may peace be upon him) having given exemption of ‘ariyya transactions measuring less than five wasqs or up to five wasqs (the narrator Dawud is in doubt whether it was five or less than five).