Ibn Umar reported that the Prophet ﷺ said, "Whoever concludes a sale and it has been finalized for him retains the option regarding it against the other party as long as they have not parted. If he wishes, he may take it, and if he wishes, he may leave it. But once they part, he has no option."
وابن عمر، عن النبي ﷺ قال: من ابتاع بيعا فوجب له فهو فيه بالخيار على صاحبه ما لم يفارقه، إن شاء أخذ، وإن شاء ترك. فإن فارقه فلا خيار له.
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Ibn Hibban (4914, 4915) and Hakim (2/14) narrated it, and Bayhaqi (5/270) from him, all of them from the hadith of Abu Saeed Hafs bin Ghaylan, who said, "Sulayman bin Musa related to us, from Ata bin Abu Rabah, from Ibn Abbas, and from Nafi, from Ibn Umar," and he mentioned it.I say, its isnad is hasan on account of Sulayman bin Musa, who is the Umayyad, their freedman, the Damascene, known as al-Ashdaq. There is disagreement about him, but he is one whose hadith is hasan, and his memory became confused shortly before his death. He is among the narrators relied upon by Muslim. Likewise, it contains Abu Saeed, with the unpointed sin and in diminutive form, Hafs bin Ghaylan, about whom there is also disagreement, but he too is one whose hadith is hasan, and Nasai and Ibn Majah both narrated from him.The hadith indicates the requirement of separating the bodies.