Cyril of Alexandria

But Emmanuel appeared who led with courage those who were snared. He endured for us the death of the flesh so that as Isaiah says in an evangelical way, the scattered children of God would be gathered into one … to gather, that is, to be bound together in one faith and like-mindedness. [They are] gathered by God the ruler of all through holiness and righteousness … and "brought near through the blood of Christ." … For it is through faith that understanding grows so that it is not in doubt. …

Commentary On Isaiah 4:3.45:20 ↗

Jerome

Gather together and come, draw near, you who have been saved from the nations. They have no knowledge, those who carry about their wooden idols and pray to a god who cannot save. LXX: Assemble yourselves, and come, and draw near together, ye that are saved of the Gentiles: they have no knowledge that set up the wood of their graven work, and pray to a god that cannot save. …

Commentary on Isaiah ↗

Thomas Aquinas

867. Second, where it says, assemble yourselves, he enjoins upon the Jews the calling of the gentiles, recalling their salvation: assemble yourselves, as though to hear my precept, you that are saved, liberated from the captivity to the gentiles, below: I will send of them that shall be saved, to the Gentiles (Isa 66:19); he also sets out the necessity of the calling, namely, the error of the gentiles, they have no knowledge that set up the wood of their graven work: you shall see in Babylon gods of gold, and of silver, and of stone, …

Commentary on Isaiah ↗