Exodus 28:29-30

29When Aaron goes into the Holy Place, he will wear the breastpiece. So he will carry the names of Israel's sons over his heart. And the Lord will always remember to bless the Israelites.

30Put the Urim and Thummim in the pocket of the breastpiece. They will also be over Aaron's heart when he goes in there to serve the Lord. The Urim and Thummim will always be there to show Aaron what the Lord is saying about the Israelites. He will carry this help over his heart all the time.