Sunan an-Nasa'i 4479

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

Reference

Sunan an-Nasa'i 4479

In-book

Book 44, Hadith 31