Musannaf Ibn Abi Shayba 13:2616

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Abd al-Aziz ibn Rufay’, from Ibn Abi Mulaykah, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The two parties to a transaction have the option (to rescind or confirm) as long as they have not separated."