Albert Barnes Commentary Psalms 45:6

"Thy throne, O God, is for ever and ever: A sceptre of equity is the sceptre of thy kingdom." — Psalms 45:6 (ASV)

Thy throne, O God, is forever and ever - This passage is quoted by the author of the Epistle to the Hebrews in proof that the Messiah is exalted above the angels, and it is, beyond all question, adduced by him as having original reference to the Messiah. See the passage explained at length in the notes at Hebrews 1:8.

I do not perceive, after an interval of nearly twenty years since those notes were written, that it is necessary to alter or to add anything to what was said there in explanation of the passage. It is undoubtedly an address to the “king” here referred to as God—as one to whom the name “God”—אלהים 'Elohiym—may be properly applied; and, as applied to the Messiah by the author of the Epistle to the Hebrews, it clearly proves that Christ is Divine.