Sahih al-Bukhari 2185
Sahih al-Bukhari · Book 34: Sales and Trade · The sale called Al-Muzabana; which is the sale of dried dates for fresh ones (that are still on the trees), and dried grapes for fresh grapes and the sale called Al-‘Araya (i.e., the selling of ripe fresh date, still over the palms, by means of estimation, for dry dates).
Narrated `Abdullah bin `Umar:
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ ، أَخْبَرَنَا مَالِكٌ ، عَنْ نَافِعٍ ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ ـ رضى الله عنهما ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى عَنِ الْمُزَابَنَةِ. وَالْمُزَابَنَةُ اشْتِرَاءُ الثَّمَرِ بِالتَّمْرِ كَيْلاً، وَبَيْعُ الْكَرْمِ بِالزَّبِيبِ كَيْلاً.
Allah's Messenger (ﷺ) forbade Muzabana; and Muzabana means the selling of fresh dates (on the trees) for dried dates by measure and also the selling of fresh grapes for dried grapes by measure.