Musannaf Ibn Abi Shayba 13:2460

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from Abu ‘Attab, from Abu Zur’ah: That he sold a horse, then he gave his companion the choice [to rescind or confirm] after the sale. Then he said: I heard Abu Hurayrah saying: "The sale is only by mutual consent."