A rich mediation by T. Austin-Spark:
If any man is in Christ, he is a new creature: the old things are passed away; behold, they are become new. But all things are of God. (2 Corinthians 5:17,18 ASV)
The all-inclusive rule of the new creation is that “all things are of (out from) God.” Concerning this fact the Apostle Paul uses the word “but” – “But all things are of God” – as though he would anticipate, intercept, or arrest an impulse to rush away and attempt life or service upon an old creation basis, or with old creation resource. The great question then is: What does it mean that all things in this new creation are out from God? What kind of a life will such a life be? To answer that question adequately would be a very comprehensive task and the most revolutionary thing conceivable.
To begin with, we should have to be settled regarding the difference between the old and the new creations, and then as to how far-reaching that difference is. In addition, we should need to see that God has put these two creations asunder, utterly and forever, and however gracious and forbearing He may be with us in our ignorance and slowness of apprehension, He never accepts the overlapping or intertwining of the two. Then there would be the further need of an inward, intelligent judgment and power by which we are made aware of the Divine veto upon the one and energy toward the other….
It is not what is done for God that will last, but what is done by God. The measure of spiritual value is determined by the measure in which God promotes it, not the measure of human activities according to human judgments and energies in the name of God.