Ibn 'Umar (Allah be pleased with them) reported Messenger of Allah ﷺ having forbidden Muzabana, and Muzabana implies the selling of dry dates for fresh dates on the tree with a definite measure (making it clear) that in case it increases, it belongs to me and if it is less, it is my responsibility. (Using translation from Muslim 1542e)
أَنَّ رَسُولَ اللهِ ﷺ نَهَى عنِ الْمُزَابَنَةِ وَالْمُزَابَنَةُ أَنْ يُبَاعَ مَا فِي رُءُوسِ النَّخْلِ بِتَمْرٍ بِكَيْلٍ مُسَمًّى إِنْ زَادَ فَلِي وَإِنْ نَقَصَ فَعَلَيَّ