Musnad Ahmad 27:618

He said: I found in my father’s book: Yazid narrated to us, Shu’bah informed us, from Abu Ishaq, from a man from Najran, that he asked Ibn ‘Umar and said: "I am only asking you about two things: about raisins and dates, and about the *salam* (forward sale) of palm trees." Ibn ‘Umar said: A drunk man was brought to the Messenger of Allah, may Allah bless him and grant him peace, and he said: "I only drank raisins and dates." He said: So he whipped him with the prescribed punishment, and he forbade that they be mixed together. He said: A man made a *salam* contract for the palm trees of a man, and he said: "His palm trees did not bear fruit that year." So he wanted to take back his dirhams, but he did not give them to him. He was brought to the Messenger of Allah, may Allah bless him and grant him peace. He said: "Did his palm trees not bear fruit?" He said: "No." He said: "Then why do you withhold his dirhams?" He said: So he handed them over to him. He said: And the Messenger of Allah, may Allah bless him and grant him peace, forbade the *salam* contract in palm trees until their ripeness becomes apparent.