John Gill Commentary Ezekiel 28:6

"therefore thus saith the Lord Jehovah: Because thou hast set thy heart as the heart of God," — Ezekiel 28:6 (ASV)

Therefore thus says the Lord God

Now follows the punishment threatened, because of all this pride, haughtiness, and blasphemy: because you have set your heart as the heart of God; seeking your own glory; setting up yourself above all others; assuming that to yourself which belongs to God; and making yourself equal to him, or showing yourself as if you were God; (See Gill on Ezekiel 28:2).