(63) باب السَّلَفِ فِي الثِّمَارِ
It was narrated that Abu Al-Minhal said:
"I heard Ibn 'Abbas say: 'When the Prophet came (to al-Madinah), they used to pay in advance for dates, two or three years in advance. He forbade them that and said: 'whoever pays in advance for dates, let him pay for a known amount or a known weight, to be delivered at a known time'''
Reference: Sunan an-Nasa'i 4616
In-book reference: Book 44, Hadith 168
English translation: Vol. 5, Book 44, Hadith 4620