Sahih al-Bukhari Book 34, Hadith 68
We were accompanying the Prophet (ﷺ) on a journey and I was riding an unmanageable camel belonging to 'Umar (ra), and I could not bring it under my control. So, it used to go ahead of the party and 'Umar would check it and force it to retreat, and again it went ahead and again 'Umar forced it to retreat. The Prophet (ﷺ) asked 'Umar to sell that camel to him. 'Umar replied, "It is for you O Allah's Messenger !" Allah's Messenger (ﷺ) told 'Umar to sell that camel to him (not to give it as gift). So, 'Umar sold it to Allah's Messenger (ﷺ). Then the Prophet (ﷺ) said to 'Abdullah bin 'Umar "This camel is for you O 'Abdullah (as a present) and you could do with it whatever you like."
The Prophet (ﷺ) said, "Both the buyer and the seller have the option of canceling or confirming the bargain unless they separate." The sub-narrator, Hammam said, "I found this in my book: 'Both the buyer and the seller give the option of either confirming or canceling the bargain three times, and if they speak the truth and mention the defects, then their bargain will be blessed, and if they tell lies and conceal the defects, they might gain some financial gain but they will deprive their sale of (Allah's) blessings."
I bartered my property in Khaibar to 'Uthman (chief of the faithful believers) for his property in Al-Wadi. When we finished the deal, I left immediately and got out of his house lest he should cancel the deal, for the tradition was that they buyer and the seller had the option of canceling the bargain unless they separated. When out deal was completed, I came to know that I have been unfair to 'Uthman, for by selling him my land I caused him to be in a land of Thamud, at a distance of three days journey from Al-Madina, while he made me neared to Al-Madina, at a distance of three days journey from my former land.