6. “Thy throne, O God, is for ever and ever.” To whom can this be spoken but our Lord ? The Psalmist cannot restrain his adoration. His enlightened eye sees in the royal Husband of the church. God, God to be adored, God reigning, God reigning everlastingly. Blessed sight! Blind are the eyes that cannot see God in Christ Jesus! We never appreciate the tender condescension of our King in becoming one flesh with his church, and placing her at his right hand, until we have fully rejoiced in his essential glory and deity. What a mercy for us that our Saviour is God, for who but a God could execute the work of salvation? What a glad thing it is that he reigns on a throne which will never pass away, for we need both sovereign grace and eternal love to secure our happiness. Could Jesus cease to reign we should cease to be blessed, and were he not God, and therefore eternal, this must be the case. No throne can endure for ever, but that on which God himself sitteth.
The Treasury of David Vol. 1 (Peabody, Maryland; The Hendrikson Publisher; 1988) p. 315 – Commentary on Psalm 45:6.