It is narrated from Sayyiduna Sahl bin Abi Hathmah that the Prophet (peace and blessings be upon him) forbade the sale of ripe fruit in exchange for fruit still on the tree, and permitted the purchase of ‘Araya by estimation so that its owner’s family could also eat fresh dates.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16092