Sunan an-Nasa'i 4470
سنن النسائي#4470SahihIt 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! "(Sahih)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiHasan
In-book reference: 44:22