Numbers 19:19
And the clean person shall sprinkle upon the unclean on the third day, and on the seventh day: and on the seventh day he shall purify himself, and wash his clothes, and bathe himself in water, and shall be clean at even.
Cross-reference
Numbers 19:12 gives the same purification instruction with the condition of the third day — directly parallel and complementary.
Numbers 19:7 details the priest's own washing and bathing after the heifer ceremony — same procedure as the unclean person's.
Numbers 19:10 applies washing clothes and uncleanness until evening to the ash gatherer — identical rule.
Numbers 31:19 applies the same third and seventh day purification to those who touched slain in battle — a direct parallel.
Numbers 8:7 uses the 'water of purification' for Levite cleansing — same purifying agent as in Num 19.
Numbers 31:24 requires washing clothes on the seventh day after battle — parallels the seventh-day purification in Num 19:19.
Hebrews 10:22 combines 'sprinkled' and 'washed' — directly echoing the purification steps in Numbers 19:19 for spiritual cleansing.