Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Do not hold back milk in the udders of camels and goats. Whoever buys (such an animal) after that has two options after milking it: if he wishes he may keep the animal, or he may return it; if he returns it, he should give a sa' of dates along with it."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10736