Sunan Ibn Majah, Chapter: The Chapters on Business Transactions

"I said to Abdullah bin Umar: 'Can I pay in advance for a date palm before it bears fruit?' He said: 'No.' I said: 'Why not?' He said: 'A man paid in advance for a grove of trees during the time of the Messenger of Allah (saw), before they had produced any fruit, and they did not bear anything that year. The purchaser said: 'They belong to me until they produce but the seller said: 'I only sold the trees to you for this year! They referred their dispute to the Messenger of Allah who said to the seller: 'Did he take anything from your date palms?' He said: 'No.' He said: 'Then why do you regard his wealth as lawful for You? Give back what you took from him, and do not take payment in advance for date palms until their usefulness appears."'