Yahya bin Ayyub said: When Abu Zur'ah made a sale with a man, he would give him the option, then he would say: Give me the option as well. And he would say: I heard Abu Hurayrah (may Allah be pleased with him) say that the Messenger of Allah (peace and blessings be upon him) said: "Two parties to a sale must not part from each other except with mutual consent."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10446