Numbers 19:9; Numbers 19:17

9 'Now a man who is clean shall gather up the ashes of the heifer and deposit them outside the camp in a clean place, and the congregation of the sons of Israel shall keep it as water to remove impurity; it is purification from sin.

17 '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.