Eliezer ben Hurcanus ruled that the calf (, "eglah") prescribed in had to be no more than one year old and the red cow (, "parah") prescribed in had to be two years old. But the Sages ruled that the calf could be even two years old and the red cow could be three or four years old. Rabbi Meir ruled that the red cow could be even five years old, but they did not wait with an older cow, as it might in the meantime grow some black hairs and thus become invalid.