Aaron and his sons must wear them whenever they enter the Tent of Meeting or approach the altar to minister in the Holy Place, so that they will not incur guilt and die. This is to be a permanent statute for Aaron and his descendants.
KJV
And they shall be upon Aaron, and upon his sons, when they come in unto the tabernacle of the congregation, or when they come near unto the altar to minister in the holy [place]; that they bear not iniquity, and die: [it shall be] a statute for ever unto him and his seed after him.
ASV
and they shall be upon Aaron, and upon his sons, when they go in unto the tent of meeting, or when they come near unto the altar to minister in the holy place; that they bear not iniquity, and die: it shall be a statute for ever unto him and unto his seed after him.