I asked Ibn ʿAbbas about Salam for (the fruits of) date-palms. He replied "The Prophet ﷺ forbade the sale a dates on the trees till they became fit for eating and could be weighed." A man asked what to be weighed (as the dates were still on the trees). Another man sitting beside Ibn ʿAbbas replied, "Till they are cut and stored." Narrated Abu Al-Bakhtari: I heard Ibn ʿAbbas (saying) that the Prophet ﷺ forbade ... etc. as above.  

نَهَى النَّبِيُّ ﷺ عَنْ بَيْعِ النَّخْلِ حَتَّى يُؤْكَلَ مِنْهُ وَحَتَّى يُوزَنَ فَقَالَ الرَّجُلُ وَأَىُّ شَىْءٍ يُوزَنُ قَالَ رَجُلٌ إِلَى جَانِبِهِ حَتَّى يُحْرَزَ وَقَالَ مُعَاذٌ حَدَّثَنَا شُعْبَةُ عَنْ عَمْرٍو قَالَ أَبُو الْبَخْتَرِيِّ سَمِعْتُ ابْنَ عَبَّاسٍ ؓ نَهَى النَّبِيُّ ﷺ مِثْلَهُ