In my last post, we began to explore a Woe to the Rebellious Children ~ Part 2 in Yesha’hayu 30:12-29. In this post, we conclude our investigation of a Woe to the Rebellious Children ~ Part 3 in Yesha’hayu 30:27-33.
Recall from our previous study that the rebellious children were Adonai’s chosen people who sought help from Egypt rather than relying on Adonai.
The prophecy in verses 27-33 describes Adonai’s appearance as a judging warrior. The object of His wrath is not revealed until verse 31, where Ashur, the oppressor of God’s people, is named.
27 Here comes the name of Adonai from afar, His anger burning, in thick rising smoke. His lips are full to the brim with fury, His tongue a consuming fire. 28 His breath is like a racing torrent that rises up to the neck, to sift the nations with the sieve of destruction, and put a bridle in the peoples’ mouths to lead them astray.
Adonai‘s anger is described in human terms as if He had lips, tongue, breath, and neck. He is hot with anger. He will take the wayward nations and bridle them as if they were a donkey or horse. Then He will guide them in the way He wants them to go.
There were two types of sieves used by Israeli farmers gave them different results. One had large holes that caught stones and other large objects as the worker shifted it back and forth. The sieve of destruction in this passage had smaller holes and was meant to separate the smaller items from the grain through a swift up-and-down motion. This makes an excellent metaphor for Adonai’s act of judgment.
29 Your song will be like one that is sung on a night when a holy feast is kept, and your hearts will be happy, as if walking to the sound of the flute, to the mountain of Adonai, to the Rock of Isra’el.
The scene shifts to the people of Adonai who will celebrate this act of God. The judgment of their enemies is a cause for rejoicing. They will praise Adonai as if it were a holy feast like Pesach or Sukkot. The mountain of Adonai refers to Tziyon where Adonai (their Rock, a title that signifies shelter and protection) will make His presence known.
30 Adonai will make his glorious voice heard, and he will reveal his arm descending with furious anger in a flaming firestorm, with cloudbursts, tempests, and hailstones.
Adonai often uses weather as His weapons against the objects of His anger.
31 For Adonai’s voice will terrify Ashur, as with His scepter He strikes them down.
Adonai’s voice is powerful. Ashur, the region’s superpower, will be punished.
Jon Courson opines:
This speaks not only of that local situation but also of the end times yet to come, for Ashurim was also a name for the antichrist, the charismatic world figure who will seek to dominate the planet. Like the Ashurim army of old, however, antichrist, too, will be beaten down. 
32 Every sweep of the punishing rod that Adonai imposes on him will be to tambourines and lyres, as He brandishes His arm against them in battle.
The blows of weapons are compared to the beating of tambourines. Bavel was the appointed punishing rod of Adonai to bring down Ashur in the late seventh century BCE.
33 For the Tofet fire pit has long been ready, prepared for the king, made large and deep, with plenty of wood and blazing with fire; like a stream of sulfur, Adonai’s breath sets it aflame. ~ Isaiah 30:27-33 (CJB)
Tofet was in the Valley of Ben-Hinnom (Jeremiah 7:30-34). This valley was immediately south and west of Yerushalayim. At times, it functioned as a garbage heap for the city. In Greek, this valley was known as Gehenna, which became associated with hell. Before King Josiah’s (one of the good kings) reforms, it had been a place where the foreign god Molech was worshiped. Jeremiah said it epitomized the sin and guilt of the people. Adonai explicitly had forbidden human sacrifice as well as the worship of Molech. Here though it is being used for a good purpose – the burning of the body of the king of Ashur after his defeat.
In my next post, we move on to unpack another woe, this time a Woe to Those Who Rely on Egypt in Yesha’hayu 31.
 Jon Courson’s Application Commentary Old Testament Volume 2.