כִּ֤י הֶֽהָרִים֙ יָמ֔וּשׁוּ וְהַגְּבָע֖וֹת תְּמוּטֶ֑נָה וְחַסְדִּ֞י מֵאִתֵּ֣ךְ לֹֽא־יָמ֗וּשׁ וּבְרִ֤ית שְׁלוֹמִי֙ לֹ֣א תָמ֔וּט אָמַ֥ר מְרַחֲמֵ֖ךְ יְהוָֽה׃ (ס)
For the mountains may depart, and the hills be removed; but My kindness shall not depart from thee, neither shall My covenant of peace be removed, saith the LORD that hath compassion on thee.
Read kabbalistic (mystical) interpretation of Isaiah 54:10: and classical mystical sources.