It was a narrated from Ayyub, from Nafi from Ibn 'Umar that the Messenger of Allah said:

"The Messenger of Allah said: "The two parties to a transaction both have the choice who long as they have not separated or one of them says to the other: 'Decide!"' (Sahih )

أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا عَبْدُ الأَعْلَى، قَالَ حَدَّثَنَا سَعِيدٌ، عَنْ أَيُّوبَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏

‏ الْبَيِّعَانِ بِالْخِيَارِ مَا لَمْ يَفْتَرِقَا أَوْ يَقُولَ أَحَدُهُمَا لِلآخَرِ اخْتَرْ ‏

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