Isaiah refers to this same highway (or sometimes just "way") all throughout the book. The highway is called the Highway of Holiness in Isaiah 35:8.
See Isaiah 11:16, 19:23, 35:8, and 40:3 about this highway.
Also Isaiah 49:11 and 62:10 mention a highway.
Isaiah 30:21 may even refer to it:
"Your ears will hear a word behind you, "This is the way, walk in it," whenever you turn to the right or to the left."
But Isaiah 35:8 is the passage that mentions the highway of holiness. All those passages I believe mention the same eschatalogical highway in Isaiah.
God Bless,
~Josh
Ok, I see where you are coming from. In many of Isaiah's verses he pairs way[h1870] with highway[h4546]. In these cases 'the way of holiness' describes the manner of one's walk while 'highway' describes the path their walk allows them to take. The straight and narrow, if you will, yet exalted because of the destination.
Isa 35:8 ¶ And an highway[h4547] shall be there, and a way[h1870], and it shall be called The way[h1870] of holiness; the unclean shall not pass over it; but it [shall be] for those: the wayfaring men, though fools, shall not err [therein].
Isa 40:3 ¶ The voice of him that crieth in the wilderness, Prepare ye the way[h1870] of the LORD, make straight in the desert a highway[h4546] for our God.
Isa 49:11 - And I will make all my mountains a way[h1870], and my highways[h4546] shall be exalted.
Isa 62:10 ¶ Go through, go through the gates; prepare ye the way[h1870] of the people; cast up, cast up the highway[h4546]; gather out the stones; lift up a standard for the people.
Isa 30:21 - And thine ears shall hear a word behind thee, saying, This [is] the way[h1870], walk ye in it, when ye turn to the right hand, and when ye turn to the left.
A metaphor for the lost's way of life (clearly a contrast to the holiness highway):
Isa 33:8 - The highways[4546] lie waste, the wayfaring man ceaseth: he hath broken the covenant, he hath despised the cities, he regardeth no man.
Isa 59:7 - Their feet run to evil, and they make haste to shed innocent blood: their thoughts [are] thoughts of iniquity; wasting and destruction [are] in their paths[4546].
Yet sometimes a highway is just a highway:
Isa 7:3 ¶ Then said the LORD unto Isaiah, Go forth now to meet Ahaz, thou, and Shearjashub thy son, at the end of the conduit of the upper pool in the highway[4546] of the fuller's field;
Isa 36:2 - And the king of Assyria sent Rabshakeh from Lachish to Jerusalem unto king Hezekiah with a great army. And he stood by the conduit of the upper pool in the highway[4546] of the fuller's field.
Which leaves:
Isa 11:16 - And there shall be an highway[h4546] for the remnant of his people, which shall be left, from Assyria; like as it was to Israel in the day that he came up out of the land of Egypt.
This refers to a metaphorical escape route for those of the lost tribes of Israel to eventually return from their diaspora at the hands of Assyria, because Israel didn't take a physical highway in their deliverance from Egypt.
Isa 19:23 ¶ In that day shall there be a highway[h4546] out of Egypt to Assyria, and the Assyrian shall come into Egypt, and the Egyptian into Assyria, and the Egyptians shall serve with the Assyrians.
Isaiah 19 illustrates a prophetic judgment on Egypt in which their future (our past) works for the glory of God. The Achaemenid Empire conquered Egypt several years after taking Babylon, who had taken Judah shortly after taking Assyria, who took Israel among others. In other words, the entire region was consolidated under one ruler whose dominion would be linked by highways. Thus Egypt, Assyria, and Israel were all serving God's plan, though in different ways.
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