What does Isaiah 26:21 mean?

The storm is coming, bringing the Lord's justice. Isaiah is assuring his readers, the people of the Lord, that the Lord is alive and active. The prophet wants to ensure his readers understand that one day God will one day step out of eternity and into time to hold humanity accountable for all its wrongdoing. The picture of the Lord arriving to deliver this justice is both terrifying and comforting (Revelation 19:11–15). We all long for justice. Our hearts desire for those who have shed innocent blood to be held accountable, and for all those who have done evil to pay for their crimes. Isaiah is clear that moment is coming.

Terror comes because we also know, deep down, that we are guilty of sin as well. We deserve judgment ourselves. None of us is righteous on our own (Romans 3:10). All of us have sinned and have fallen short of God's glory (Romans 3:23). We have only one hope of escaping the terrible judgment of the Lord when all sin is revealed on the earth: "the righteousness of God through faith in Jesus Christ for all who believe" (Romans 3:22).

Paul spells it out: "For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord" (Romans 6:23). Only those who have received that gift (Titus 3:5) will be excluded from God's act of judgment followed by "shame and everlasting contempt (Daniel 12:2)." As Paul also declares:

"If you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved. For the Scripture says, 'Everyone who believes in him will not be put to shame' " –Romans 10:9–11.