Leviticus 10:6-7

6Then Moses said to Aaron and to his [younger] sons Eleazar and Ithamar, “Do not uncover your heads nor let your hair hang loose nor tear your clothes [as expressions of mourning], so that you will not die [also] and so that He will not express His wrath and anger toward all the congregation. But your relatives, the whole house of Israel, may mourn the burning which the Lord has brought about.

7You shall not even go out of the doorway of the Tent of Meeting, or you will die; for the Lord’s anointing oil is upon you.” So they did [everything] according to the word of Moses.