مسند امام احمد بن حنبل · Hadith 5129

Abu Ishaaq (said): I heard a man from Najraan say: I asked Ibn 'Umar, saying: I shall only ask you two things: about selling the crop of a palm tree for immediate payment before it is clearly ripe (Salam transaction) and about raisins and dates. He said - An intoxicated man was brought to the Messenger of Allah (PBUH) he had drunk (a mixture of) raisins and dates. He had him flogged as the hadd punishment, and he forbade mixing them. And a man bought the crop of another man's date palms in a salam transaction (In which payment was made Immediately for something to be deliered later), then his palm trees did not bear any fruit. He (the buyer) came to him to ask for his money back, but he refused to give it to him. They went to the Prophet (ajg) who said: "Did your palm trees bear fruit?" He said: No. He said: "Then why aie you keeping his money?" And he instructed him to return it to him and he did. And (the Prophet (PBUH)) forbade salam transactions with regard to date palms until the fruit is fully ripe.