Numbers 19:17
And for an unclean person they shall take of the ashes of the burnt heifer of purification for sin, and running water shall be put thereto in a vessel:
Cross-reference
Numbers 19:9
Parallel
In Numbers 19:9, the ashes of the red heifer are stored for purification; Numbers 19:17 instructs using those ashes — a direct internal cross-reference.
Numbers 19:12
Parallel
Numbers 19:12 instructs using this water for purification on the third and seventh days — a direct continuation of the same law.
Numbers 8:7
Parallel
Numbers 8:7 prescribes the same 'water of cleansing' for Levites, directly parallel to the ritual here.
Numbers 31:23
Parallel
Numbers 31:23 references the same 'water of cleansing' for purifying plunder after fire — a direct cross-reference.