"The two parties to a transaction have the choicer so long as they have not separated, unless they reach an agreement before parting, and it is not permissible to hasten to leave for fear that the other party may change his mind."  

أَنَّ النَّبِيَّ ﷺ قَالَ الْمُتَبَايِعَانِ بِالْخِيَارِ مَا لَمْ يَتَفَرَّقَا إِلاَّ أَنْ يَكُونَ صَفْقَةَ خِيَارٍ وَلاَ يَحِلُّ لَهُ أَنْ يُفَارِقَ صَاحِبَهُ خَشْيَةَ أَنْ يَسْتَقِيلَهُ