It was narrated from Ayyub, from Nafi from Ibn 'Umar, who said:

"The Messenger of Allah said: 'The two parties to a transaction both have the choice so long as they have not separated or chosen to conclude the transaction." Or perhaps Nafi said: "Or one of them has said to the other: 'Decide! "

أَخْبَرَنَا زِيَادُ بْنُ أَيُّوبَ، قَالَ حَدَّثَنَا ابْنُ عُلَيَّةَ، قَالَ أَنْبَأَنَا أَيُّوبُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ ﷺ " الْبَيِّعَانِ بِالْخِيَارِ حَتَّى يَفْتَرِقَا أَوْ يَكُونَ بَيْعَ خِيَارٍ " . وَرُبَّمَا قَالَ نَافِعٌ " أَوْ يَقُولَ أَحَدُهُمَا لِلآخَرِ اخْتَرْ " .