‘I have sewed sackcloth upon my skin’ – this graphic expression describes what Job had done to cover himself, sowing sackcloth, not to his skin, but around his skin. The action of putting on sackcloth was often joined with rending one’s garment (Job 1:20) as an expression of mourning.
For each one of us, prayer must start with a time of consulting our consciences to see what is known there, what must first be confessed and repented of. We should humble ourselves greatly before the Lord when we experience dire circumstances and strong trials. We must search our hearts to see if there is some cause in ourselves for our suffering. We do so because God is calling us to solemn humility and we know the tendency of the flesh to rise up in complaint and therefore do all we can to suppress this.
‘What led Job to do this [to weep and sow sackcloth upon his skin and cover his head with dust]? … It is true that those who think little about God, do not fail to complain greatly and weep and howl, but they will never wear sackcloth in a right way unless they have an eye to God. Although hypocrites do not rightly know God, they have some conception of him when they show such signs of repentance, and are forced to admit that God is their judge. But since Job did it sincerely we say that he was not benumbed as these unbelievers are. If God handles them roughly, they think only of the misfortune that has happened to them. Job did not behave like this. He was fully resolved to attribute all these things to God … Let us come to God’s law and pray to him to enlighten us with his Holy Spirit that we may search out our own darkness, for the sins that are in us are terrible lurking holes’ (Calvin – English updated).