"Ye shall have a song, as in the night when a holy solemnity is kept; and gladness of heart, as when one goeth with a pipe to come into the mountain of the LORD, to the mighty One of Israel. And the LORD shall cause his glorious voice to be heard, and shall shew the lighting down of his arm, with the indignation of his anger, and with the flame of a devouring fire, with scattering, and tempest, and hailstones."
A direct translation of the first part would read, "The song shall become to you as a night of a consecrated (holy) festival." Israel will have a definite song in the day of her redemption. The Feast of Tabernacles was an exalted feast to the Jews and is mentioned with high regard in the Scriptures. This holy festival is perhaps pictured here seeing it had both day and nighttime ceremonies. In the kingdom, attendance at the Feast of Tabernacles will be required for all nations (Zechariah 14:16). The mighty One is literally Rock. The same title for the Lord is used in Deuteronomy 32:4 where God is named the Rock. Having hearts changed by the Spirit of Christ, both Jew and Gentile will gladly make their way to Jerusalem where they will worship the Rock of Israel in sincerity (Isaiah 2:2-3).
On that fearful night of Sennacherib's punishment, the Lord brought down His arm of judgment upon the Assyrian army. In similar fashion, His mighty arm of judgment will intercede against the enemies of Israel at the fall of the antichrist's kingdom when "The LORD ... shall roar out of Zion, and utter his voice from Jerusalem (Joel 3:16)."
"For through the voice of the LORD shall the Assyrian be beaten down, which smote with a rod. And in every place where the grounded staff shall pass, which the LORD shall lay upon him, it shall be with tabrets and harps: and in battles of shaking will he fight with it. For Tophet is ordained of old; yea, for the king it is prepared; he hath made it deep and large: the pile thereof is fire and much wood; the breath of the LORD, like a stream of brimstone, doth kindle it."
Once again Isaiah's familiar message is proclaimed. Only through the Lord's power can the enemy be defeated. This principle holds true for Israel today. Struggle as she may, she will never deliver herself from the oppression of her enemies. Only by divine intervention can Israel be saved.
The word behind grounded means foundation. The word behind staff is simply another term for rod. While the terminology is a bit odd, the idea seems to be the destruction of the Assyrian army followed by the triumphant cries of Israel. In every place where the rod of Assyria passed in defiance of God, Israel would come behind and rejoice over her destruction. Shaking literally means waving. The picture is that of a warrior wielding his weapon, killing and wounding the enemy with every stroke. The sword of the Lord would destroy the enemy with every blow and exultant songs of praise to the Lord would follow in the aftermath. This very picture is presented in the prophecies of the end times. The sword of the Messiah will be unsheathed against the enemies of Jerusalem, and the Lord's people will follow behind with songs of humble worship (Zechariah 14).
Tophet was in the valley of Hinnom on the south end of Jerusalem. In this place was burned the rubbish of the city and even the dead bodies of criminals. Here, the Lord uses this familiar valley as a picture of hell's fires (Mark 9:44-48). This valley may have served as an actual burying place for many Assyrian soldiers; however, it stands mainly as a symbol for the fearful fate of the one who rejects God's authority and chooses his own way. Gehenna (which is pictured by Tophet) eventually served as Sennacherib's final destination. At Christ's return, this same place of torment will ensnare the antichrist and his followers. The fiery valley of Tophet is not reserved only for the extremely wicked. Any individual outside of Jesus Christ will be sent there, because sin's judgment is satisfied only through faith in Christ's position as Savior and God.
The chapter ends with another encouraging message for the one who seeks the Almighty. God is a God of judgment, and keeping promises is part of righteous judgment. Over and over again, the Lord promises to deliver the one who will, in faith, wait for Him.
Wait on the LORD: be of good courage, and he shall strengthen thine heart: wait, I say, on the LORD (Psalm 27:14).