جامع الترمذي

Narrated 'Amr bin Shu'aib:

From his father, from his grandfather, that the Messenger of Allah (ﷺ) said: "Both the buyer and the seller retain the option as long as they did not separate, unless they agreed to making it optional. And it is not lawful for him to separate from his companion, fearing that he will change his mind."

[Abu 'Eisa said:] This Hadith is Hasan and this means separating from him after the sale, fearing that he will change his mind. And if the separation referred to speech, and there was no option left for him after the sale, then this Hadith would be meaningless, since he (ﷺ) said: "And it is not lawful for him to separate from his companion, fearing that he will change his mind."