It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah Almighty be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever buys a musarrah sheep (one whose milk has been held back in its udder), if he is pleased with it, (he keeps it); otherwise he should return it, and give a sa' of dates along with it."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10001