Maliks Muwatta Book 31, Hadith Number 14.
Yahya related to me from Malik from Nafi from Abdullah ibn Umar from Zayd ibn Thabit that the Messenger of Allah, may Allah bless him and grant him peace, allowed the holder of an ariya to barter the dates on the palm for the amount of dried dates it was estimated that the palms would produce.
Yahya related to me from Malik from Da’ud ibn al-Husayn from Abu Sufyan, the mawla of Ibn Abi Ahmad, from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, allowed the produce of an ariya to be bartered for an estimation of what the produce would be when the crop was less than five awsuq or equal to five awsuq. Da’ud wasn’t sure whether he said five awsuq or less than five.
Malik said, “Ariyas can be sold for an estimation of what amount of dried dates will be produced. The crop is examined and estimated while still on the palm. This is allowed because it comes into the category of delegation of responsibility, handing over rights, and involving a partner. Had it been like a form of sale, no one would have made someone else a partner in the produce until it was ready nor would he have renounced his right to any of it or put someone in charge of it until the buyer had taken possession.”