Leviticus 21:4-6

The Voice

⁴ A priest must not render himself impure and defile himself by touching the corpse of a person related to him only by marriage. ⁵ Priests are not allowed to mourn like other people by shaving their heads, trimming their beards, or cutting gashes into their bodies. ⁶ Priests are to be holy to Me and not treat My sacred name with contempt. They bring the fire-offerings to Me, the food of their God, and so they must be sacred.