"When two people meet to engage in trade, the transaction between them is not binding until they separate, unless they have chosen to conclude the transaction." (Using translation from Nasāʾī 4476)
أَنَّهُ سَمِعَ رَسُولَ اللهِ ﷺ يَقُولُ «كُلُّ بَيِّعَيْنِ فَلَا بَيْعَ بَيْنَهُمَا حَتَّى يَتَفَرَّقَا إِلَّا بَيْعَ الْخِيَارِ»