Tirmidhi

‘Abdullah bin ‘Umar (may Allah be pleased with both of them) says: I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: “The seller and the buyer both have the option (to cancel or confirm the sale) as long as they have not separated, or they both stipulate the option.” Nafi‘ says: When Ibn ‘Umar (may Allah be pleased with both of them) would buy something and was sitting, he would stand up so that the sale would become binding (and the option would no longer remain).

Imam Tirmidhi says:
1- The hadith of Ibn ‘Umar (may Allah be pleased with both of them) is Hasan Sahih.
2- In this chapter, there are also ahadith from Abu Barzah, Hakim bin Hizam, ‘Abdullah bin ‘Abbas, ‘Abdullah bin ‘Amr, Samurah, and Abu Hurairah (may Allah be pleased with them).
3- Some of the people of knowledge from among the Companions and others have acted upon this. And this is also the saying of Shafi‘i, Ahmad, and Ishaq bin Rahwayh. These people say that by separation is meant physical separation, not verbal separation, i.e., leaving the gathering is meant, not changing the subject of conversation.
4- And some of the people of knowledge say that by the saying of the Prophet (peace and blessings of Allah be upon him) «مالم يتفرقا» is meant verbal separation. The first opinion is more correct, because Ibn ‘Umar (may Allah be pleased with both of them) himself narrated this from the Prophet (peace and blessings of Allah be upon him), and he knows best the meaning of the hadith he narrated. And it is narrated from him that when he intended to make the sale binding, he would (leave the gathering and) walk away so that the sale would become binding.
5- It is also narrated in the same way from Abu Barzah (may Allah be pleased with him).

Hakim bin Hizam (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The seller and the buyer have the option (to cancel or confirm the sale) as long as they do not separate. 1 Both have the right to keep the sale or to annul it. If both speak the truth and make clear the good and bad aspects of the goods, there will be blessing in their sale. But if they conceal defects and tell lies, the blessing of their sale will be erased." © Imam Tirmidhi says:
1- This hadith is authentic.
2- Similarly, it is also narrated from Abu Barzah Aslami that two men, after selling a horse, brought their case to him while they were in a boat. Abu Barzah said: "I do not think that you both have separated, and the Messenger of Allah (peace and blessings of Allah be upon him) said: 'The seller and the buyer have the option as long as they do not separate (from the gathering).' "
3- Some scholars among the people of Kufa and others have held the view that separation is by statement, and this is also the saying of Sufyan Thawri, and similarly it is narrated from Malik bin Anas.
4- And Ibn Mubarak said: "How can I reject this view when an authentic hadith has been reported from the Prophet (peace and blessings of Allah be upon him)?"
5- And he has declared it strong. The meaning of the saying of the Prophet (peace and blessings of Allah be upon him) «إلا بيع الخيار» is that after the sale becomes binding, the seller gives the buyer the option, then when the buyer chooses the sale, after that he will not have the option to annul the sale, even if they have not separated. Similarly, Shafi'i and others have interpreted it.
6- And the view of those who say that separation is physical (separation of bodies) is supported by the hadith of Abdullah bin Amr, which he narrates from the Prophet (peace and blessings of Allah be upon him) (which is coming ahead).

‘Abdullah bin ‘Amr (may Allah be pleased with them both) reports that the Messenger of Allah (peace and blessings of Allah be upon him) said: “The seller and the buyer have the option (to cancel the transaction) as long as they have not separated, unless it is a transaction with a stipulated option (khiyar), in which case the right of return remains even after separation. And it is not permissible for the seller to separate from his companion (the buyer) out of fear that he will cancel the sale.” © Imam Tirmidhi says:
1- This hadith is Hasan (good),
2- And its meaning is that after the sale, he separates from the buyer out of fear that he will cancel it, and if separation were only by speech, and the buyer had no option after the sale, then this hadith would have no meaning, which is what you (the Prophet) said: “It is not permissible for the seller to separate from the buyer out of fear that he will cancel his sale.”