The details provided for the priestly garments that Aaron and his sons were to wear when ministering to God show us the perfection he requires. Every detail of its elaborate design is included in the scriptures. They could not go before God in everyday clothes; he expected more from them. These garments were those of royalty, studded with precious stones in settings of gold and engraved with the names of the sons of Israel.
No one can go before God in old clothes; he expects perfection! We are not perfect; however, we have a Priest who ministers before the Holy of Holies on our behalf, much like Aaron did for the Israelites. However, our Priest is pure from the inside out without flaw or blemish. Jesus is our perfection, and God sees us as holy because of him.
And these are the garments which they shall make; a breastplate, and an ephod, and a robe, and a broidered coat, a mitre, and a girdle: and they shall make holy garments for Aaron thy brother, and his sons, that he may minister unto me in the priest's office. Exodus 28:4