The Divine ordinance of purification through the ashes of the RED HEIFER, as outlined in the book of Numbers, chapter 19
Biblical law is concerned with several types of impurity which have a direct affect on everyday life, especially when the Holy Temple is standing. The most severe type of impurity is that which is caused by exposure to death. There are several methods for restoring purity, most notably immersion in water - but the Torah's exclusive antidote to the impurity of death is purification by sprinkling of the red heifer's ashes. Many of the thousands who arrived at the Holy Temple had to undergo this process before they could enter into the Court.
The ordinance of the red heifer has detailed requirements which must be met. Some of these are directly relayed in the Biblical verses of Numbers chapter 19; many others were transmitted orally to Moshe and than passed down by the rabbis throughout the generations, until the present day. These are expounded upon in the writings of the Oral Tradition.
The heifer must be three years old and perfect in its redness. This means that the presence of as few as two hairs of any other color will render it invalid; it is related that for this reason, the red heifer was always very expensive to procure. Even its hooves must be red. It must also be totally free from any physical blemish or defect, whether internal or external.
Although the red heifer is not a sacrifice per se, for it is not slaughtered in the Temple, it is forbidden that the heifer should possess any of those blemishes which render any sacrifice invalid - such as those enumerated in the book of Leviticus, chapter 22. The red heifer also has an additional, unique requirement: it must have never been used to perform any physical labor. In fact, using the animal in any physical sense at all would render it invalid, even for the slightest, most minor thing. This would include riding, or even leaning on her. The only exception would be some labor which is intrinsically necessary for the heifer's own welfare, such as tying her for her own safety. But if a yoke were placed upon her even once, even if she were not used to plow - this would be enough to render the heifer unfit for use. Thus Scripture states, "that a yoke never went on."
The commandment calls for the animal to be a "heifer," that is, 3 or 4 years old; although an older animal could also be used. Since the verse instructs us to take a heifer, we do not purchase a calf and wait for it to grow older while in our custody; "and take a heifer" means that the act of acquisition has to take place while the animal is a heifer. However, if a red calf is available, a price can be set with its owner, and the transaction can be concluded, but we do not take possession until it reaches the proper age as mandated by the Torah.
The animal which meets these requirements and others could be used to fulfill the commandment of providing the ashes for the purification process. This heifer must be brought to the "Mount of Anointment," a precise location on the Mount of Olives, opposite the eastern gate of the Temple Mount. There the heifer must be slaughtered and burned. Afterwards, its ashes are mixed together with natural spring water. It is this solution, called by Torah "the waters of sanctification," which is used to sprinkle on those who are impure.