The Messenger of Allah ﷺ said, "Two parties must not part except by mutual agreement."
قال رسول الله ﷺ: لا يفترقن اثنان إلا عن تراض.
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This was narrated by Abu Dawud (3458), Tirmidhi (1248), and Bayhaqi (2715) from the hadith of Yahya bin Ayub, who said, Abu Zura, whenever he concluded a sale with a man, would give him the choice. He said, then he would say, "Give me the choice," and he would say, "I heard Abu Hurairah say," and then he related it. Its chain is hasan because of Yahya bin Ayub, who is the Bajali, the Kufan, for he is hasan al-hadith. As for Tirmidhi, he said, "a gharib hadith."Something of similar meaning was reported from Abu Hurairah, who said, The Messenger of Allah ﷺ said, "Both parties to a sale have the choice as long as they have not separated, or until their transaction concludes with a choice." This was narrated by Ahmad (8099), Tabarani in al-Awsat (908), Tayalisi (2691), and Tahawi in Sharh Mushkil (5411), all of them through the route of Ayub bin Utba, from Abu Kathir al-Ghubari, from Abu Hurairah, who related it. Ayub bin Utba is the Yamami, Abu Yahya the judge, and he is daif by the agreement of the scholars. The hadith of Abu Hurairah has other chains as well, but they are all daif.The legal point of this chapter: it can be deduced from these hadiths that what is meant by "separation" is physical separation of the bodies, as Ibn Umar, Ibn Abbas, and other companions understood it. This is also the position of Ahmad, Shafii, and the majority of the scholars of hadith. Malik and Abu Hanifa said that once the contract is concluded, the sale is valid whether the two parties separate or not.