The Messenger of Allah ﷺ was asked about exchanging dried dates for fresh dates. He asked those around him, "Do fresh dates decrease in volume when they become dry?"They replied, "Yes."So he forbade it.
أخبرنا عمرو بن علي قال حدثنا يحيى قال حدثنا مالك قال حدثني عبد الله بن يزيد عن زيد بن أبي عياش
سئل رسول الله ﷺ عن التمر بالرطب فقال لمن حوله أينقص الرطب إذا يبس قالوا نعم فنهى عنه
[Its isnad is hasan] Abu Dawud narrated it in the Book of Trade, Chapter on Fresh Dates for Dried Dates, no. 3359, Tirmidhi, no. 1225, and Ibn Majah, no. 2264, from the hadith of Malik through this route. It is also found in Muwatta (Yahya): 2/624, and in Kubra, no. 6136. Tirmidhi said, "hasan sahih." Ibn Jarud graded it sahih, no. 657, as did Hakim, 2/38-39, and Dhahabi agreed with him.