Hadith: The Prophet (may Allah's peace and blessings be upon him) forbade the sales called Mukhābarah, Muhāqalah, Muzābanah and the selling of fruits until they are fit for eating. He also forbade the selling of fruits but for money, except in the case of ‘Araya

عن جابر بن عبد الله رضي الله عنهما مرفوعاً: نهى النبي صلى الله عليه وسلم عن المُخَابَرَةِ والمُحَاقَلَةِ، وعن المُزَابنة، وعن بيع الثَّمَرَة حتى يَبدُو صَلاحُها، وأن لا تبُاع إلا بالدينار والدرهم، إلا العَرَايَا.
[صحيح] - [متفق عليه]

Jābir ibn ‘Abdullāh (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) forbade the sales called Mukhābarah, Muhāqalah, Muzābanah and the selling of fruits until they are fit for eating. He also forbade the selling of fruits but for money, except in the case of ‘Araya.
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

The Prophet (may Allah's peace and blessings be upon him) forbade some of the sales of crops because of the harm they incur on one or both sides of the transaction (buyer and seller). These sales include Mukhābarah, which is to lease out land in return for the produce of a specified part of the land; Muhāqalah, which is to sell wheat in the ear in return for husked wheat (wheat separated from the chaff); Muzābanah, which is to sell dates on palm trees in return for dates. He also forbade selling fruit until its condition becomes clear that it is free from blight and good for eating, but he made an exception for ‘Araya (date-palms), i.e. ripe dates after their value is estimated, in return for the same value of fruit.