Isaiah 4:3-4

The divine judgments that God will bring on the Israelites in the future (in the Tribulation) will have a purifying effect on many of them, specifically the elect (cf. Isaiah 1:25; Ezekiel 36:25-26; Ezekiel 39:23-26; Daniel 9:4-19; Malachi 3:2-5; Matthew 3:11; Acts 13:48). Those left alive to the end will be holy in conduct, as well as set apart by God for His purposes. Similarly, God purified the Israelites through their oppression in Egypt and then liberated them so they could be a holy nation (Exodus 19:6)-in calling and in conduct. In both cases God Himself did it. This purification was only true to a very limited extent of those Israelites who returned from the Exile, as the post-exilic books of the Old Testament reveal.

The "daughters of Zion" throughout this oracle represent all the Israelites, not just the females in the nation (cf. Isaiah 3:16-17). The "spirit" in view (Isaiah 4:4) is probably the abstract concept of "process" (cf. Isaiah 19:14; Isaiah 28:6; Isaiah 29:10; Isaiah 37:7). A less probable view is that the spirit is the Holy Spirit.