Verse 30 is a typical Isaianic reversal. Rather than the first-born of the rich, it will be the first-born of the poor who will have food. Rather than the wealthy being safe, it will be the needy who “lie down in safety.” This reversal occurs because the destructive intent of the conquering army is against the upper classes, not the poor. The poor are relatively safe because they are not seen as a threat.
Continuing the metaphor of the “root” to symbolize Philistia’s past rulers, Yahweh announces that they will starve in a famine, possibly a reversal of the “first-born of the poor shall feed.” Probably the famine results from warfare, for while the “root” dies in the famine, the “remnant,” or descendants, will be slain, presumably by the sword.