Albert Barnes Commentary Job 21:5

"Mark me, and be astonished, And lay your hand upon your mouth." — Job 21:5 (ASV)

Mark me – Margin, "look to." Literally, "Look upon me." That is, look attentively at me, at my sufferings, at my disease, and at my losses. See if I am a proper object of reproach and mockery—see if I do not have abundant reason to be in deep distress when God has afflicted me in such an unusual and mysterious manner.

And be astonished – Silent astonishment should be shown instead of censure. You should wonder that a man whose life has been one of piety should exhibit the spectacle that you now behold, while so many proud despisers of God are permitted to live in affluence and ease.

And lay your hand upon your mouth – As a sign of silence and wonder. So Plutarch, de Iside et Osiride, “Therefore, he had laid his finger on his mouth as a symbol of silence and admiration—ἐχεμυθίας καὶ σιωπῆς σύμβολον echemuthias kai siōpēs sumbolon.”