Numbers 19:10

And he that gathereth the ashes of the heifer shall wash his clothes, and be unclean until the even: and it shall be unto the children of Israel, and unto the stranger that sojourneth among them, for a statute for ever.

Cross-reference

Numbers 19:7 also describes the priest becoming unclean after handling the heifer, mirroring the gatherer's uncleanness.

Numbers 19:8 states the burner of the heifer becomes unclean, same pattern as the gatherer in verse 10.

Numbers 19:19 shows the sprinkler also washes and becomes unclean until evening, parallel to the gatherer's ritual uncleanness.

Numbers 15:15 declares one law for native and stranger, matching the same inclusive statute in Numbers 19:10.

Leviticus 11:25 gives the identical rule for washing clothes and uncleanness until evening after touching unclean carcasses.

Leviticus 15:5 also requires washing clothes and uncleanness until evening, here after touching a bed of someone with a discharge.