سنن النسائي

It was narrated from Ayyub, from Nafi from Ibn 'Umar, who said: "The Messenger of Allah (ﷺ) 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 )