Muwatta Imam Malik Book of Business Transactions, Hadith 80

Yahya related to me from Malik from Nafi from Abdullah ibn Umar that the Messenger of Allah ﷺ said, "Both parties in a business transaction have the right of withdrawal as long as they have not separated, except in the transaction called khiyar."
Malik said, "There is no specified limit nor any matter which is applied in this case according to us."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " الْمُتَبَايِعَانِ كُلُّ وَاحِدٍ مِنْهُمَا بِالْخِيَارِ عَلَى صَاحِبِهِ مَا لَمْ يَتَفَرَّقَا إِلاَّ بَيْعَ الْخِيَارِ " .