Charles H. Spurgeon on Psalms 50:21

Thou thoughtest that I was altogether such an one as thyself. This men do when they plead for sins as little, as venial, as that which is below God to take notice of; because they themselves think it so, therefore God must think it so too. Man, with a giant like pride, would climb into the throne of the Almighty, and establish a contradiction to the will of God by making his own will, and not God's, the square and rule of his actions. This principle commenced and took date in Paradise, where Adam would not depend upon the will of God revealed to him, but upon himself and his own will, and thereby makes himself as God. Stephen Charnock.