Musannaf Ibn Abi Shayba 13:2609

Abu Bakr narrated to us, he said: Jarir ibn Abd al-Hamid narrated to us, from Abd al-Aziz ibn Rufay, from Ibn Abi Mulaykah and Ata, they both 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) as long as they have not separated by mutual consent."