Allah's Messenger (ﷺ) appointed somebody as a governor of Khaibar. That governor brought to him an
excellent kind of dates (from Khaibar). The Prophet (ﷺ) asked, "Are all the dates of Khaibar like this?" He
replied, "By Allah, no, O Allah's Messenger (ﷺ)! But we barter one Sa of this (type of dates) for two Sas of
dates of ours and two Sas of it for three of ours." Allah's Messenger (ﷺ) said, "Do not do so (as that is a kind
of usury) but sell the mixed dates (of inferior quality) for money, and then buy good dates with that
money."
Sahih al-Bukhari Book 34, Hadith 148