Narrated Ibn 'Umar (RA):

Allah's Messenger (ﷺ) 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. [Agreed upon]. Narrated Sa'd bin Abu Waqqas (RA): I heard Allah's Messenger (ﷺ) 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. [Reported by al-Khamsah and graded Sahih (authentic) by Ibn al-Madini, at-Tirmidhi, Ibn Hibban and al-Hakim].

وَعَنْ اِبْنِ عُمَرَ ‏-رَضِيَ اَللَّهُ عَنْهُمَا‏- قَالَ: { نَهَى رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-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 } مُتَّفَقٌ عَلَيْهِ [1]‏ .‏ 845 ‏- وَعَنْ سَعْدِ بْنِ أَبِي وَقَّاصٍ ‏- رضى الله عنه ‏- قَالَ: { سَمِعْتُ رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-سُئِلَ عَنِ اِشْتِرَاءِ اَلرُّطَبِ بِالتَّمْرِ.‏ فَقَالَ: أَيَنْقُصُ اَلرُّطَبُ إِذَا يَبِسَ? " قَالُوا: نَعَمَ.‏ فَنَهَى عَنْ ذَلِكَ } رَوَاهُ اَلْخَمْسَةُ, وَصَحَّحَهُ اِبْنُ اَلْمَدِينِيِّ, وَاَلتِّرْمِذِيُّ, وَابْنُ حِبَّانَ, وَالْحَاكِمُ [2]‏ .‏