Albert Barnes Commentary Isaiah 4:3

"And it shall come to pass, that he that is left in Zion, and he that remaineth in Jerusalem, shall be called holy, even every one that is written among the living in Jerusalem;" — Isaiah 4:3 (ASV)

He who is left in Zion - This properly refers to the remnant that would remain after the mass of the people would be cut off by wars, or be carried into captivity. If it refers to the few that would come back from Babylon, it means that they would be reformed, and would be a generation different from their fathers—which was undoubtedly true. If it refers, as the connection seems to indicate, to the times of the Messiah, then it speaks of those who are left, while the great mass of the nation would be unbelievers, and would be destroyed. The mass of the nation would be cut off, and the remnant that was left would be holy; that is, all true friends of the Messiah would be holy.

Shall be called holy - That is, will be holy. The expression to be called is often used in the Scriptures as synonymous with to be.

Everyone who is written among the living - The Jews were accustomed to register the names of all the people. Those names were written in a catalogue, or register, of each tribe or family. To be written in that book, or register, meant to be alive, for when a death occurred, the name was struck out (Exodus 32:32; Daniel 12:1; Ezekiel 13:9).

The expression also came to denote all who were truly the friends of God—those whose names are written in his book, the book of life. In this sense, it is used in the New Testament (Philippians 4:3; Revelation 3:5; Revelation 17:5).

It is understood this way in this place by the Chaldee Paraphrase: "Everyone will be called holy who is written to eternal life; he will see the consolation of Jerusalem." If the reference here is to the Messiah, then the passage denotes that under the reign of the Messiah, all who would be found enrolled as His followers would be holy.

An effectual separation would subsist between them and the mass of the people. They would be enrolled as His friends, and they would be a separate, holy community (Compare 1 Peter 2:9).