Sayyiduna Zayd bin Thabit (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) granted a concession in the 'araya sale, that "the fruit on the tree may be sold by estimation for a known measure."
(b) 'Araya were specific known date palms; he would come to those palms and buy it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10662