The Prophet (s.a.w) said: "The two parties of a transaction have the right (to annul the contract) as long as they donot seperate (from each other). So, if they were truthful (to one another), and honest in exaplaining (the defects of an item), then they will be blessed in their transaction. But, if they lied, and hid (the defects of an item) then the blessings of their transaction are destroyed"
[Muslim,3836]
