Musannaf Ibn Abi Shayba 13:524

Abu Bakr narrated to us, he said: Abu Usamah narrated to us, from Hisham, from al-Hasan, that he used to see no harm in a *salam* (forward sale) for a known term, whether its principal was with him or not. He said: And Muhammad used to dislike *salam* except for something whose principal was with its owner.