Sahih Muslim Book 10, Hadith Number 3642.

Chapter : It is invalid to sell the commodity before taking possession of it.

Ibn Abbas (Allah be pleased with them) reported Allah’s Messenger (may peace be upon him) as saying: He who buys food-rain should not sell it until he has taken possession of it. Ibn Abbas (Allah be pleased with them) said: I regard everything like food (so far as this principle is concerned).