Isaiah 4:3

He that is left in Zion

The holy remnant

“Holy” means what is separated from the world and superior to it; the congregation of the saints, or holy ones, who now inhabit Jerusalem, are what remain after a smelting; their holiness is the consequence of a washing.

(F. Delitzsch.)

God has never yet left the world without a nucleus of heaven

He has drowned the world, but left a seed to build an altar; He has burned the Gomorrahs of the world, but He has allowed the faithful to escape, and to become the beginning of a new progeny. There is always a remnant, the one left, the true heart, the faithful among the faithless found. (J. Parker, D. D.)

Holiness becomes the Christian

We are told that the little creature called the ermine is so sensitive to its own cleanliness that it becomes paralysed and powerless at the slightest touch of defilement upon its snow-white fur. A like sensibility should belong to the Christian, who should abstain from the very appearance of evil. (Sunday School Chronicle.)