וְנָתַתָּ֞ אֶל־חֹ֣שֶׁן הַמִּשְׁפָּ֗ט אֶת־הָאוּרִים֙ וְאֶת־הַתֻּמִּ֔ים וְהָיוּ֙ עַל־לֵ֣ב אַהֲרֹ֔ן בְּבֹא֖וֹ לִפְנֵ֣י יְהוָ֑ה וְנָשָׂ֣א אַ֠הֲרֹן אֶת־מִשְׁפַּ֨ט בְּנֵי־יִשְׂרָאֵ֧ל עַל־לִבּ֛וֹ לִפְנֵ֥י יְהוָ֖ה תָּמִֽיד׃ (ס)
And thou shalt put in the breastplate of judgment the Urim and the Thummim; and they shall be upon Aaron’s heart, when he goeth in before the LORD; and Aaron shall bear the judgment of the children of Israel upon his heart before the LORD continually.
Read kabbalistic (mystical) interpretation of Exodus 28:30: and classical mystical sources.