וְכִפֶּ֤ר אַהֲרֹן֙ עַל־קַרְנֹתָ֔יו אַחַ֖ת בַּשָּׁנָ֑ה מִדַּ֞ם חַטַּ֣את הַכִּפֻּרִ֗ים אַחַ֤ת בַּשָּׁנָה֙ יְכַפֵּ֤ר עָלָיו֙ לְדֹרֹ֣תֵיכֶ֔ם קֹֽדֶשׁ־קָֽדָשִׁ֥ים ה֖וּא לַיהוָֽה׃ (פ)
And Aaron shall make atonement upon the horns of it once in the year; with the blood of the sin-offering of atonement once in the year shall he make atonement for it throughout your generations; it is most holy unto the LORD.’
Read kabbalistic (mystical) interpretation of Exodus 30:10: and classical mystical sources.