John Calvin Commentary Isaiah 57:20

"But the wicked are like the troubled sea; for it cannot rest, and its waters cast up mire and dirt." — Isaiah 57:20 (ASV)

But the wicked. Having previously spoken of the “peace” which good men will enjoy, he threatens that the wicked, on the contrary, will have continual war and incessant uneasiness and distress of heart. This is so that good men may value more highly the excellent blessing of “peace,” and also, so that the reprobate may know that their condition will in no way be improved because of that peace which is promised to the children of God.

But because the reprobate make false claims to the name of God and vainly boast in it, the Prophet shows that there is no reason for them to flatter themselves or make any claim based on this promise, since they can have no share in this peace. Nor will it benefit them at all that God, having compassion on his people, receives them into favor and commands peace to be proclaimed to them.

As the troubled sea. That metaphor of “the sea” is elegant and very well suited to describe the uneasiness of the wicked, for in itself “the sea is troubled.” Though it is not beaten by the wind or agitated by frightful tempests, its billows carry on mutual war and dash against each other with terrible violence.

In the same way, wicked men are “troubled” by inward distress, which is deeply seated in their hearts. They are terrified and alarmed by conscience, which is the most agonizing of all torments and the most cruel of all executioners.

The furies agitate and pursue the wicked, not with burning torches (as the fables say), but with anguish of conscience and the torment of wickedness. For everyone is distressed by his own wickedness and his own alarm; everyone is agonized and driven to madness by his own guilt; they are terrified by their own evil thoughts and by the pangs of conscience.

Therefore, the Prophet has most appropriately compared them to a stormy and troubled sea. Whoever then wishes to avoid these alarms and this frightful agony of heart, let him not reject that peace which the Lord offers him. There can be no middle course between them; for, if you do not lay aside sinful desires and accept this peace, you must unavoidably be miserably distressed and tormented.