Qatada قتادة · The Chapters on Business Transactions

"The Messenger of Allah (ﷺ) said: 'It is not permissible to sell something that is not with you, nor to profit from what you do not possess."'

"There is no contractual obligation after four (days)."

"There is no one who deals in usury a great deal (to increase his wealth) but he will end up with little (i.e., his wealth will be decreased)."

"Abdullah bin Shaddad and Abu Barzah had a dispute about paying in advance. They sent me to 'Abdullah bin Abu Awfa to ask him about it. He said: 'We used to make payments in advance at the time of the Messenger of Allah (ﷺ) and the time of Abu Bakr and 'Umar, for wheat, barley, raisins and dates, to people who did not yet possess those things.' I asked Ibn Abza, and he said something similar."