I exchanged some silver for gold with Talhah bin ‘Ubaidullah, and he said: Wait for me until our storekeeper comes from al-Ghabah, "Umar bin al-Khattab heard that and said: No, by Allah! Do not leave him until you take your exchange from him, for I heard the Messenger of Allah (ﷺ) say: "Gold for silver is riba unless it is "here, take this" and "here, take this" [i.e., exchanged on the spot].”