Consider it holy to the Lord

 Exodus 30:17-38;37:29

It will be the sacred anointing oil. Then use it to anoint the tent of meeting, the ark of the covenant law, the table and all its articles, the lampstand and its accessories, the altar of incense, the altar of burnt offering and all its utensils, and the basin with its stand. You shall consecrate them so they will be most holy, and whatever touches them will be holy.

Whoever makes perfume like it and puts it on anyone other than a priest must be cut off from their people.

Then the Lord said to Moses, “Take fragrant spices—gum resin, onycha and galbanum—and pure frankincense, all in equal amounts, and make a fragrant blend of incense, the work of a perfumer. It is to be salted and pure and sacred. Grind some of it to powder and place it in front of the ark of the covenant law in the tent of meeting, where I will meet with you. It shall be most holy to you. Do not make any incense with this formula for yourselves; consider it holy to the Lord. Whoever makes incense like it to enjoy its fragrance must be cut off from their people.”

Why?

The incense does not the incense-like other religions, it is not for the general people to worship their gods, it is the incense to show the Lord is with his people. It is holy to the Lord. So whoever makes incense like it will be cut off from their people.

Same as the sacred anointing oil is holy, only the priest can use it and used it in the altar and the lamp in the altar.

How?

God is holy so everything that relates to the Lord has to be holy. We need to live in the Holy Christian life.