Exodus 28:29-30

29“Whenever Aaron goes into the holy place, he will be carrying the names of the sons of Israel over his heart as a constant reminder in the Lord’s presence. He must do this by wearing the breastplate for decision-making.

30Put the Urim and Thummim  into the breastplate for decision-making. They, too, will be over Aaron’s heart when he comes into the Lord’s presence. In this way whenever he’s in the Lord’s presence, Aaron will always be carrying over his heart the ⌞means for determining the Lord’s⌟ decisions for the Israelites.