John Calvin Commentary Isaiah 1:28

"But the destruction of transgressors and sinners shall be together, and they that forsake Jehovah shall be consumed." — Isaiah 1:28 (ASV)

And the destruction of the transgressors. So that hypocrites do not imagine that any fruit of these promises belongs to them, and indulge in vain boasting, he threatens that they will perish, even if God redeems His Church. For hypocrites have always been mingled with the Church, and indeed are connected with it most closely; but they base their judgment of it on outward appearances.

All that God promises they immediately and confidently apply to themselves. The apostle tears this trust from them—if indeed it deserves the name of trust, which springs from pride and the arrogance of a haughty mind.

Here we should observe how great wisdom godly teachers need, so that, while they terrify the wicked with the judgment of God, they may at the same time support good men and strengthen them with some consolation, so that they are not cast down and discouraged. On the other hand, when believers are encouraged by the promise of God, and when wicked men falsely apply it to themselves and puff themselves up with vain confidence, the method and course we should follow is that we neither give wicked men reason to become proud, nor depress or discourage the godly, as Isaiah does in this passage.

For while he speaks of the redemption of the Church, he at the same time threatens that sinners (that is, wicked men) will be destroyed, so that they do not suppose that these acts of God’s kindness belong at all to them.

Yet, while he pronounces destruction against the wicked, by this comparison he exhibits more fully the favor of God toward believers. This favor is seen far more distinctly when God allows the reprobate to perish but preserves His own in safety, as it is said:

A thousand shall fall at thy side, and ten thousand at thy right hand; but it shall not come nigh thee. (Psalms 91:7)

Besides, he mitigates the grief and anguish that the decrease in the Church's numbers might produce in godly minds, for he shows that the only way to impart health to the whole body is by removing its corruption.