Water of lustration
The water of lustration or water of purification was the water created with the ashes of the red heifer, according to the instructions given by God to Moses and Aaron in the Book of Numbers.
Biblical references
The Hebrew Bible taught that any Israelite who touched a corpse, a Tumat HaMet, was ritually unclean. The water was to be sprinkled on a person who had touched a corpse, on the third and seventh days after doing so, in order to make the person ritually clean again. A tent in which someone had died was similarly considered to be unclean.The water was to be used as follows:
The water was used again in for the purification on the metallic booty brought back by the Israelites following their victory over the Midianites.
In other biblical translations the water is referred to as water of expiation, water of separation, water of cleansing or water for impurity. The Jerusalem Bible uses the term lustral water. In Hebrew, the water was called mei niddah by the Torah and mei chatat by Chazal.