Sahih Bukhari Volume 3, Book 35, Hadith 2250

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا غُنْدَرٌ، حَدَّثَنَا شُعْبَةُ، عَنْ عَمْرٍو، عَنْ أَبِي الْبَخْتَرِيِّ، سَأَلْتُ ابْنَ عُمَرَ ـ رضى الله عنهما ـ عَنِ السَّلَمِ، فِي النَّخْلِ فَقَالَ نَهَى النَّبِيُّ صلى الله عليه وسلم عَنْ بَيْعِ الثَّمَرِ حَتَّى يَصْلُحَ، وَنَهَى عَنِ الْوَرِقِ بِالذَّهَبِ نَسَاءً بِنَاجِزٍ،وَسَأَلْتُ ابْنَ عَبَّاسٍ فَقَالَ نَهَى النَّبِيُّ صلى الله عليه وسلم عَنْ بَيْعِ النَّخْلِ حَتَّى يَأْكُلَ أَوْ يُؤْكَلَ، وَحَتَّى يُوزَنَ‏.‏ قُلْتُ وَمَا يُوزَنُ قَالَ رَجُلٌ عِنْدَهُ حَتَّى يُحْرَزَ‏

Narrated By Abu Al-Bakhtari : I asked Ibn 'Umar about Salam for dates. Ibn 'Umar replied, "The Prophet forbade the sale (the fruits) of date-palms until they were fit for eating and also forbade the sale of silver for gold on credit." I also asked Ibn 'Abbas about it. Ibn 'Abbas replied, "The Prophet forbade the sale of dates till they were fit for eating, and could be weighed." I asked him, "What is to be weighed (as the dates are on the trees)?" A man sitting by Ibn 'Abbas said, "It means till they are cut and stored."