In that day He will punish Leviathan, and slay the great dragon in the sea. NKJV says reptile, but the KJV and the Hebrew Bible in English say “dragon.” I believe this is a direct reference to the great dragon of Revelation, the ancient enemy of God, who will be slain by the breath of His mouth in “that day.”
This is a fulfillment of the first prophecy of the Bible:
“And I will put enmity
Between you and the woman,
And between your seed and her Seed;
He shall bruise your head,
And you shall bruise His heel.” Gen 3:15
The LORD spoke these words to Satan, the serpent who tempted Eve. It is this reptile, this dragon, who has been the cause of leading astray into sin from the beginning, and the LORD indicates to Isaiah that not only will the iniquities of the earth be punished, but the root from which those iniquities sprang, will be punished and slain.
Israel is His vineyard which produces choice wine! This figure has been used before in Isaiah. Concerning the punishment which is coming on Israel, the LORD is saying that as a vinedresser He cares for His vineyard. He does not take any actions against it in fury, i.e. without restraint, and even when He must remove His enemies from His vineyard by strong measures, if they take hold of Him and make peace with Him, then even His enemies will be at peace.
Those who come He shall cause to take root in Jacob;
Israel shall blossom and bud,
And fill the face of the world with fruit. Isa 27:6
Those who were His former enemies, shall come to Him and make peace with Him (Rom 5:8-10), and He shall root them in Jacob and graft them in (Rom 11:16-24), and Israel shall be like a luxurious vine rooted in their land, but whose fruit fills the whole earth.
The LORD is saying that even though He struck Israel, by sending them into captivity, Ephraim to Assyria and Judah to Babylon (which of course, was still a future event in Isaiah’s day), He has not struck him to slay him as He has struck His enemies to slay them. But He has struck him in moderation (NKJV, “in measure,” vs. 8), and by sending him away by the east wind, i.e., eastward to captivity, it will have the result of taking away his sin of idolatry. While Israel is in captivity, the stones of the idol altars will become like chalkstones, i.e., easily ground to powder till nothing of them is left.
The fortified cities of Israel will be desolate during that time, for the people that formerly dwelt in them will be taken away. Don’t let Israel think that because the LORD is merciful, He will relent of this punishment; they lack understanding, therefore this punishment will come upon them. For they have shown by repeated return to their besetting sin of idolatry, that nothing less than captivity will purge them of it.
Israel may be removed, but they will be returned to their land. For YHVH is the great husbandman. When the time of captivity has ended, the LORD will beat the trees from the River Euphrates (Assyria) to the Nile (Egypt), as a farmer beats his trees in harvest time, and the LORD will gather His fruit, the children of Israel, even one by one so that not one is forsaken.
The great trumpet might refer to the trumpet blast of the angel on the Day of Trumpets; at any rate, the trumpet was blown in Israel as a call to gather together before the LORD. So those who are left in Assyria and left in Egypt will come and gather together before the LORD in Jerusalem, to worship Him.
It is interesting that these last two verses mention the three nation axis of Israel, Assyria, and Egypt; we saw before that they will join together to worship the LORD (Isa 19:23-24). It makes me wonder if these two verses in Isa 27 are a matching pair in a chiastic structure with Isa 19:23-24. For further study!