Numbers 19:15

Overview - Numbers 19
The water of separation made of the ashes of a red heifer.
11 The law for the use of it in purification of the unclean.
Treasury of Scripture Knowledge

Numbers 19:15  (King James Version)
And every open vessel, which hath no covering bound upon it, is unclean.

31:20 Leviticus 11:32 ; 14:36