Commentaries
31:16-23 Job's conscience gave testimony concerning his just and charitable behaviour toward the poor. He is most large upon this head, because in this matter he was particularly accused. He was tender of all, and hurtful to none. Notice the principles by which Job was restrained from being uncharitable and unmerciful. He stood in awe of the Lord, as certainly against him, if he should wrong the poor. Regard to worldly interests may restrain a man from actual crimes; but the grace of God alone can make him hate, dread, and shun sinful thoughts and desires.
22. Apodosis to Job 31:13, 16, 17, 19, 20, 21. If I had done those crimes, I should have made a bad use of my influence ("my arm," figuratively, Job 31:21): therefore, if I have done them let my arm (literally) suffer. Job alludes to Eliphaz' charge (Job 22:9). The first "arm" is rather the shoulder. The second "arm" is the forearm.
from the bone—literally, "a reed"; hence the upper arm, above the elbow.