Albert Barnes Commentary Job 31:22

"Then let my shoulder fall from the shoulder-blade, And mine arm be broken from the bone." — Job 31:22 (ASV)

Then let my arm—The strong language Job uses here shows his consciousness of innocence and his detestation of the offences to which he here refers (Job 31:16–22). The word rendered “arm” here (כתף kâthêph) properly means the shoulder (Isaiah 46:7; Isaiah 49:22; Numbers 7:9; compare the notes at Isaiah 11:14). It is believed there is no instance, unless this is one, in which it means arm. The meaning here is that he wished, if he had been guilty, his shoulder might separate from the blade. Herder, Rosenmuller, Umbreit, and Noyes render it so; and so do the Vulgate and the Septuagint.

From my shoulder-blade—The scapula—the flat bone to which the upper arm is attached. Job’s wish is that the shoulder might separate from that, and of course the arm would be useless. Such a strong imprecation implies a firm consciousness of innocence.

And my arm—The word “arm” here denotes the forearm—the arm from the elbow to the fingers.

From the bone—Margin: “the chanelbone.” Literally, “from the reed”—מקנה miqâneh. Umbreit renders it, Schneller als ein Rohr—quicker than a reed. The word קנה qâneh properly means a reed, cane, or calamus (see the notes at Isaiah 43:24), and is here applied to the upper arm, or arm above the elbow, from its resemblance to a reed or cane. It is also applied to the arm or branch of a chandelier or candlestick (Exodus 25:31) and to the rod or beam of a balance (Isaiah 46:6). The meaning here is that he wished his arm would be broken at the elbow, or the forearm be separated from the upper arm, if he were guilty of the sins he had specified. This probably alludes, with great force and propriety, to what he had said in Job 31:21: “If his arm had been lifted up against an orphan, he prayed that it might fall powerless.”