Exodus 28:29-31

New Revised Standard Version, Anglicised

²⁹ So Aaron shall bear the names of the sons of Israel in the breastpiece of judgement on his heart when he goes into the holy place, for a continual remembrance before the Lord. ³⁰ In the breastpiece of judgement you shall put the Urim and the Thummim, and they shall be on Aaron’s heart when he goes in before the Lord; thus Aaron shall bear the judgement of the Israelites on his heart before the Lord continually.

Other Priestly Vestments

³¹ You shall make the robe of the ephod all of blue.