Isaiah 48:4 Kabbalah

מִדַּעְתִּ֕י כִּ֥י קָשֶׁ֖ה אָ֑תָּה וְגִ֤יד בַּרְזֶל֙ עָרְפֶּ֔ךָ וּמִצְחֲךָ֖ נְחוּשָֽׁה׃

Because I knew that thou art obstinate, And thy neck is an iron sinew, and thy brow brass;