Sahih Bukhari, Chapter: Sales and Trade

The Prophet said, "Both the buyer and the seller have the option of cancelling 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 cancelling 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."