MOST OF ISAIAH 3-4 IS GIVEN OVER to specific judgment, in a kind of ABB'A' construction (Isa. 3:1-4:1), which is followed by glorious hope for the future (Isa. 4:2-6).
At the core of the condemnation is the Lord as Judge, indicting "the elders and leaders [literally, 'princes'] of his people" (Isa. 3:13-15). Royal family and local leaders ("elders") alike have descended to corruption and oppression. But the next two verses condemn the "women of Zion" as well (Isa. 3:16-17). The men are condemned primarily for oppression, the women for their vanity and ostentation. Surrounding these verses are two longer sections unfolding what the men are being condemned for (Isa. 3:1-12) and what the women's judgment will be like (Isa. 3:18-4:1).
God will bring siege and famine upon the people (Isa. 3:1), resulting in the elimination of community leaders, whether by deportation or death (Isa. 3:2-3). The entire society will break down, signaled not least by a desperate willingness to appoint almost anyone as leader (Isa. 3:5). This vision was literally fulfilled a century and a half later (2 Kings 25:1-12), but there were adumbrations within Isaiah's lifetime of what the judgment would be like: what Assyria began (Isa. 39:5-7), Babylon completed. For the culture was largely corrupt (Isa. 3:8-11), the cause lying in the leadership, which was as weak as it was oppressive (Isa. 3:12).
The siege will not be kind to the ostentatious women either (Isa. 3:18-4:1). All their finery is to be snatched away (Isa. 3:18-23). Instead of the delightful fragrances on which they have spent so much money, there will be stench. There will be disease (Isa. 3:17a), sexual abuse (Isa. 3:17b---the RSV is probably right: "the Lord will lay bare their secret parts," i.e., subject them to the sexual assaults so common in war), and bereavement (Isa. 3:25). Some will end up throwing themselves at any male available in the desperate hope for refuge and home (Isa. 4:1)---but the slaughter of males will be so terrible that there will not be enough to go around.
Often in Old Testament prophecy there is a "foreshortening" of visions of the future that runs back and forth between the near future and something much farther away. If the day of the Lord brings horrendous judgment (Isa. 3:6-4:1), it also brings glory (Isa. 4:2-6). Later, "Branch" (Isa. 4:2) will clearly be a way of referring to Messiah (Isa. 11:1; 53:2; cf. Jer. 23:5; 33:15; Zech. 3:8; 6:12), but here it seems to refer to the people and purposes of God in glorious fruitfulness. In language that calls forth images of the Exodus, God promises to wash away the filth of his people and manifest his glory as a protective shield over them (Isa. 4:4-6).