The Messenger of Allah ﷺ said, "When two men make a transaction, each of them has the option to cancel as long as they have not parted and are still together, or until one of them gives the other the choice. If they conclude the sale on that basis, the sale is binding. And if they part after concluding the transaction, and neither of them has cancelled the sale, then the sale is binding."
عن رسول الله ﷺ أنه قال: إذا تبايع الرجلان فكل واحد منهما بالخيار ما لم يتفرقا، وكانا جميعا، أو يخير أحدهما الآخر، فتبايعا على ذلك، فقد وجب البيع. وإن تفرقا بعد أن يتبايعا، ولم يترك واحد منهما البيع فقد وجب البيع.
Bukhari narrated it in the Book of Sales (2112), and Muslim in the Book of Sales (1531:44), both through the route of Layth (that is, Ibn Saad), from Nafi, from Ibn Umar, who mentioned it. Muslim also narrated it (1531:45) through the route of Sufyan bin Uyayna, from Ibn Jurayj, from Nafi, in similar fashion, adding, "Nafi said, 'If he (meaning Ibn Umar) sold something to a man and wanted him not to be able to rescind the sale, he would get up and walk a little while, then return to him.'"This is evidence that Ibn Umar held the view that what was meant by "separation" was physical separation of the bodies, not separation by words.