-The remnant of the LORD’s people is succinctly explained in this short stanza of writing. The phrase “in that day” leaves some ambiguity, but is certainly a future prophecy of a time coming when evil will be eradicated and the people of God will live in peace. It will be a day when “the Branch (Messianic reference, Jesus) will be beautiful and glorious, and the fruit of the earth will be the pride and the adornment of the survivors of Israel (Isaiah 4:1-2).” This will be a time of complete holiness by His people, the righteous remnant. These saved ones are recorded for life in Jerusalem (Isaiah 4:3, Philippians 4:3, Revelation 3:5; 20:11-15, 21:27). Note that it is the LORD who washes away the filth and purges the bloodshed by His Spirit of judgment and burning (Isaiah 4:4). He creates over the whole area of Mt. Zion a covering of cloud by day with even smoke, and the brightest of a flaming fire by night with His glory underneath. This will be His shelter to give shade from the heat by day, and refuge and protection from the storm and the rain (Isaiah 4:5-6). Cloud by day...fire by night - To the Jewish readers these allusions would bring to mind the days of wilderness wandering when the cloud and fire were tangible reminders that Jehovah was "personally" guiding and protecting His people (Exodus 13:21-22; 14:19, 24). Today we have His indwelling Spirit to guide believers.
Allan Harman comments regarding the canopy that...
The exodus experience of a pillar of fire and a pillar of cloud will be repeated. Just as Israel had the LORD’s protection when they came out of Egypt, so will a renewed and cleansed Israel/Zion. The word for ‘canopy’ or ‘covering’ (Heb. chuppâh) is only used three times in the Old Testament (Isaiah 4:5; Joel 2:16; Psalm 19:5), but it has come into modern usage as the term to describe the canopy over a couple during the Jewish marriage service. The conjunction here with the terms ‘shelter’, ‘shade’, ‘refuge’ and ‘hiding place’ make it plain that the idea is of a protective canopy that will provide shade and a shield to Mount Zion. The use of the verb ‘create’ (Heb. bârâ’) is significant because it is reserved for when God is the subject. The great Creator will act in His sovereignty to protect Zion and all the remnant who gather there.
I tend to agree with Thomas Constable's summation of this section...
This oracle (Isaiah 2:1-4:6) reveals events that would happen in a “day” yet future from Isaiah’s perspective. History has shown that some of the predictions of judgment found partial fulfillment in the exiles of Israel that preceded Messiah’s appearing. However most of the judgment, and all of the blessing connected to Messiah, lies in the future from our perspective (Matt. 24:4-30). It is mainly the Tribulation and Messiah’s blessing of Israel in the Millennium to follow that is in view here.
(references from http://preceptaustin.org/isaiah_42-6_commentary.html).
-*Application* Is your name in the Lamb’s Book of Life? If there is any question, ask the Savior, Jesus Christ, to redeem you from all sin and filth by simple faith. He can do it through His propitiatory sacrifice on the cross of Calvary and His resurrection. Jesus saves! Call upon Him and gain eternal life under God’s ultimate protection (Psalm 116:13, Acts 2:21).
Verse to Memorize: Isaiah 4:2