Musnad Abu Ya'la al-Mawsili 155:209

Hadba narrated to us, Hammad bin al-Ja'd narrated to us, Qatada narrated to us that Muhammad bin Sirin narrated to him that Abu Hurairah narrated to him that the Prophet, peace and blessings of Allah be upon him, gave a judgment regarding the *musarrah* (an animal whose milk has been withheld in the udder to deceive the buyer): If a man buys it and milks it, he has the choice: if he wishes, he may keep it, and if he wishes, he may return it along with a *sa'* of dates.