Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever buys a musarrah (an animal whose milk has been held back in its udder) has the option for three days; if he wants to return it, he may return it, and give a sa' of dates along with it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10456