Mishkat al-Masabih 2974

Hanzala b. Qais quoted Rafi‘ b. Khadij to the effect that his two paternal uncles told him they used to let out land in the time of the Prophet for what grew by the streamlets, or for something the owner of the land set aside, but the Prophet forbade them to do that. He asked Rafi’ how the matter would stand if payment were made in dirhams and dinars and he replied that there would be no harm in that. It seemed that what was prohibited was such as people versed in what is allowed and what is prohibited would not permit if they looked into it, because of the risk involved*. * The objection to such an agreement is that one cannot guarantee beforehand what a particular piece of land will produce. (Bukhari and Muslim.)