Musannaf Ibn Abi Shayba 13:3126

Abu Bakr narrated to us, he said: Yahya ibn Adam narrated to us, he said: Mufaddal narrated to us, from Mughira, who said: I said to Ibrahim: "May a man enter into a salam contract for grapes?" He saw no harm in it. I said: "May he enter into a salam contract for grapes, and take them as unripe dates (busr)?" He said: "No."