Exodus - Chapter 28

This Chapter describes the garments that were to be worn by the High Priest, including a special breastpiece.

Christians are priests and, like Aaron, need to wear the correct garments.  Paul describes our garments in Ephesians 6:

"Stand therefore, having girded your waist with truth, having put on the breastplate of righteousness, and having shod your feet with the preparation of the gospel of peace; above all, taking the shield of faith with which you will be able to quench all the fiery darts of the wicked one. And take the helmet of salvation, and the sword of the Spirit, which is the word of God."