“Why is the law of God irrevocable?  The Bible makes that plain.  Because it is rooted in the nature of God.  God is righteous and that is the reason why His law is righteous.  Can He then revoke His law or allow it to be disregarded?  Well, there is of course no external compulsion upon Him to prevent Him from doing these things.  There is none who can say to Him, ‘What doest thou?’  In that sense He can do all things.  But the point is, He cannot revoke His law and still remain God.  He cannot, without Himself becoming unrighteous, make His law either forbid righteousness or condone unrighteousness.  When the law of God says, ‘The soul that sinneth it shall die,’ that awful penalty of death is, indeed, imposed by God’s will; but God’s will is determined by God’s nature, and God’s nature being unchangeably holy the penalty must run its course.  God would be untrue to Himself, in other words, if sin were not punished; and that God should be untrue to Himself is the most impossible thing that can possibly be conceived.”

J. Gresham Machen, “The Doctrine of the Atonement,” (December 1936); Sunday radio address given three weeks prior to his death.