Sunan an-Nasa'i 4474
سنن النسائي#4474Sahihأَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ حَدَّثَنَا هُشَيْمٌ، عَنْ يَحْيَى بْنِ سَعِيدٍ، قَالَ حَدَّثَنَا نَافِعٌ، عَنِ ابْنِ عُمَرَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " الْمُتَبَايِعَانِ لاَ بَيْعَ بَيْنَهُمَا حَتَّى يَتَفَرَّقَا إِلاَّ بَيْعَ الْخِيَارِ " .
It was narrated from Yahya bin Sa 'eed , who said:"Nafi narrated to us from Ibn 'Umar, who said: 'The Messenger of Allah said: There is no transaction between the two parties until they separate, unless they have chosen to conclude the transaction."" (Sahih)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 44:26