Numbers 19:9

“Thus you shall do to them, for their cleansing: sprinkle purifying water on them, and let them use a razor over their whole body and wash their clothes, and they will be clean.

‘And you shall give it to Eleazar the priest, and it shall be brought outside the camp and be slaughtered in his presence.

‘Then for the unclean person they shall take some of the ashes of the burnt purification from sin and flowing water shall be added to them in a vessel.

everything that can stand the fire, you shall pass through the fire, and it shall be clean, but it shall be purified with water for impurity. But whatever cannot stand the fire you shall pass through the water.

For if the blood of goats and bulls and the ashes of a heifer sprinkling those who have been defiled sanctify for the cleansing of the flesh,