It was narrated that Hakim bin Hizam said:"The Messenger of Allah said: 'The two parties to a transaction have the choice so long as they have not separated. If they are honest and open, their transaction will be blessed, but if they tell lies and conceal anything, the blessing of their transaction will be lost."
أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، عَنْ يَحْيَى، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ حَدَّثَنِي قَتَادَةُ، عَنْ أَبِي الْخَلِيلِ، عَنْ عَبْدِ اللَّهِ بْنِ الْحَارِثِ، عَنْ حَكِيمِ بْنِ حِزَامٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " الْبَيِّعَانِ بِالْخِيَارِ مَا لَمْ يَفْتَرِقَا فَإِنْ صَدَقَا وَبَيَّنَا بُورِكَ فِي بَيْعِهِمَا وَإِنْ كَذَبَا وَكَتَمَا مُحِقَ بَرَكَةُ بَيْعِهِمَا " .
Nesai
The Book of Financial Transactions • Hadith 4457