وَعَنْ اِبْنِ عُمَرَ رَضِيَ اَللَّهُ عَنْهُمَا
قَالَ: «نَهَى رَسُولُ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَنِ الْمُزَابَنَةِ; أَنْ يَبِيعَ ثَمَرَ حَائِطِهِ إِنْ كَانَ نَخْلاً بِتَمْرٍ كَيْلاً، وَإِنْ كَانَ كَرْماً أَنْ يَبِيعَهُ بِزَبِيبٍ كَيْلاً، وَإِنْ كَانَ زَرْعاً أَنْ يَبِيعَهُ بِكَيْلِ طَعَامٍ، نَهَى عَنْ ذَلِكَ كُلِّهُ»
The Messenger of Allah (sallallahu alayhi wa sallam) forbade al-Muzabanah, which means that a man sells the fruit of his garden, if it consists of palm-trees (fresh dates), for dried dates by measure; or if it consists of grapes (on the vines), for raisins by measure; or if it is unpicked crops, he sells it for a measured amount of picked crops.
He forbade all that. Narrated Sad ibn Abu Waqqas (radiyallahu anhu): I heard the Messenger of Allah (sallallahu alayhi wa sallam) being asked about buying fresh dates for dry ones.
He replied, “Will fresh dates diminish when they become dry?” They answered, “Yes.” So he forbade that.