It is narrated from Sayyiduna Sa'd (may Allah be pleased with him) that he was asked about two men exchanging silt and barley with each other. Sayyiduna Sa'd (may Allah be pleased with him) said that in the time of the Noble Prophet ﷺ, two men exchanged dry and fresh dates with each other, upon which the Messenger of Allah ﷺ inquired, "Does fresh date lose weight when it dries?" The companions replied, "Yes," so then he forbade them from such a sale.
Hadith Referenceالسنن المأثورة / باب في البيوع / 203
Hadith Takhrijسنن نسائی، البيوع، باب اشتراء التمر بالرطب، رقم : 4546 وقال الالبانی: صحيح ۔