Abu Dawud
Wages
Book Number: 017 / Hadith Number: 3460
Narated By Abdullah ibn Umar : A man paid in advance for a palm-tree. It did not bear fruit that year. They brought their case for decision to the Prophet (pbuh). He said: for which do you make his property lawful? He then said: Do not pay in advance for a palm-tree till they (the fruits) were clearly in good condition.