Sahih al-Bukhari Book 34, Hadith 67
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."
The Prophet (ﷺ) said, "No deal is settled and finalized unless the buyer and the seller separate, except if the deal is optional (whereby the validity of the bargain depends on the stipulations agreed upon).
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."