Hadith
أَخْبَرَنَا عَمْرُو بْنُ يَزِيدَ، عَنْ بَهْزِ بْنِ أَسَدٍ، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ دِينَارٍ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " كُلُّ بَيِّعَيْنِ فَلاَ بَيْعَ بَيْنَهُمَا حَتَّى يَتَفَرَّقَا إِلاَّ بَيْعَ الْخِيَارِ " .
It was narrated from Shu'ban who said:"Abdullah bin Dinr narrated to us, from Ibn'Umar, who said; The Messenger of Allah said; "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
Sahih · Abu Ghuddah
Sunan an-Nasa'i 4479 ·Book 44, Hadith 31·Also available on sunnah.com·