Volume 3 · Book 34 · Hadith 402
Narrated Anas bin Malik: The Prophet forbade the sale of fruits till their benefit is evident; and the sale of date palms till the dates are almost ripe. He was asked what 'are almost ripe' meant. He replied, "Got red and yellow."
— Sahih Bukhari, Volume 3, Book 34: Sales and Trade, Hadith #402