Zirr said, I asked Ibn Abbas about the sale of date-palm fruit.He said, "The Messenger of Allah ﷺ forbade selling date-palm fruit until one can eat from it or it can be eaten, and until it is weighed."I asked, "What does 'weighed' mean?"A man sitting with him said, "Until it can be estimated."
حدثنا محمد بن جعفر حدثنا شعبة عن عمرو بن مرة
سألت ابن عباس عن بيع النخل فقال نهى رسول الله ﷺ عن بيع النخل حتى يأكل منه أو يؤكل منه وحتى يوزن قال فقلت ما يوزن فقال رجل عنده حتى يحزر
Its isnad is sahih. See 2247."Yuzan" (weighed), Ibn Athir said, it means to estimate and appraise. He called it "weighing" because the appraiser estimates it and calculates its amount, so it becomes like weighing it.The reason for the prohibition involves two matters. The first is safeguarding property, since crops are generally not safe from blight except after ripening, and that is the time of appraisal. The second is that if one sells it before its soundness has appeared, on condition that it be cut, and before appraisal, the rights of the poor in it are forfeited, since Allah made it obligatory to pay it out at the time of harvest.