Charles Ellicott Commentary James 4:12

"One [only] is the lawgiver and judge, [even] he who is able to save and to destroy: but who art thou that judgest thy neighbor?" — James 4:12 (ASV)

There is one lawgiver...—A better rendering is: One is the Lawgiver and Judge, Who is able to save and to destroy: but you—who are you that judge a neighbour? As a king is the fountain of honour, so the ultimate source of law is God; and all judgment really is delegated by Him, just as ordinary courts represent the royal majesty: to usurp such functions is to provoke the offended sovereign—whether of earth or heaven. “It is not our part,” said Bengel, “to judge, since we cannot carry out our sentence.” (Compare to a parallel scripture, Romans 14:4.)

Able to save and to destroy.—Life and death, salvation and utter destruction, seem to be placed in intentional contrast here. (Compare to Matthew 10:28.) The thought of annihilation meets us with awful suggestiveness, yet let us leave the mystery for a while in happier thought—

“That nothing walks with aimless feet;
That not one life shall be destroyed,
Or cast as rubbish to the void,
When God has made the pile complete.”