We are commanded regarding the ritual impurity contracted through contact with a human corpse. [I.e., if contracted, one must follow all the laws associated with this impurity.]
"And it shall be as a keepsake for the congregation of the children of Israel"—Numbers 19:9.
We are commanded to prepare a red heifer [as detailed in the Torah], to have it ready for the procedure of purifying those who are ritually impure as a result of contact with a corpse.