From Sahih Muslim (Hadith 3887):
Bashair b. Yasir reported on the authority of some of the Companions of Allah's Messenger (ﷺ) among the members of his family among whom one was Sahl b. Abu Hathma that Allah's Messenger (ﷺ) forbade buying of fresh dates against dry dates and that it is Riba and this is Muzabana, but he made an exemption of 'ariyya (donations) of a tree or two in which case the members of a family sell dry dates and buy fresh dates for eating them
Reference: Muslim 3887