Sahih Muslim Book 10, Hadith Number 3835.
Chapter : The sale of silver for gold is prohibited when payment is to be made in future.
Abu Sa’id al-Khudri (Allah be pleased with him) reported: I heard Allah’s Messenger (may peace be upon him) addressing in Medina. He said: O people, Allah is giving an indication (of the prohibition) of wine and he is probably soon going to give an order about it. So he who has anything of it with him should sell that, and derive benefit out of it. He (the narrator) said: We waited for some time that Allah’s Apostle (may peace be upon him) said: Verily Allah, the Exalted, has forbidden wine. So who hears this verse and he has anything of it with him, he should neither drink it nor sell it. He (the narrator) said: The people then brought whatever they had of it with them on the streets of Medina and spilt that.