The most severe of all ritual impurities is tum'at met, the impurity contracted through contact with a human corpse. This section details the purification process for an individual or object which has contracted this form of impurity. A red heifer is slaughtered and is burned together with a few added ingredients. Water from a stream is added to the ashes. On the third and seventh day after contracting tum'at met, this mixture is sprinkled upon the individual or object. After immersion in a mikvah (ritual pool), the person or object is freed of this impurity.