John Calvin Commentary Isaiah 63:4

"For the day of vengeance was in my heart, and the year of my redeemed is come." — Isaiah 63:4 (ASV)

For the day of vengeance is in my heart. In the former clause of this verse, Isaiah indicates that God does not cease to perform his duty, even though he does not instantly execute his judgments; on the contrary, he delays until a suitable time, which he knows well. Isaiah further indicates that it is not our place to prescribe to him when or how he should do this or that; rather, we should bow submissively to his decree, so that he may administer all things according to his will. Therefore, let us not imagine that he is asleep or idle when he delays.

And the year of my redeemed is come. In this latter clause, he shows that all these things are done for the sake of believers. “Day” and “year” are used by him here in the same sense, but the word “year” signifies the long duration of the captivity, so that the Jews may not despair or grow faint and weary if the redemption is long delayed. The Lord therefore punishes and destroys wicked men for the purpose of delivering the godly and redeeming his Church, for which he has a special regard.

Finally, by their slaughter and destruction, he opens a way for his grace. And this is for our consolation: whenever we see signs of God’s wrath toward the wicked, we can know that the fruit of the punishment they endure will come to us. For in this way, it is clearly shown that our groans are heard and that God, when he wishes to relieve the afflicted, is armed with strength to put to flight all the enemies of his Church. Therefore, although the cross is heavy for us, yet by patiently enduring, let us learn to lift up our minds in hope to that “year” which God has appointed for executing his vengeance.