In that day there will be an altar to the LORD in the midst of the land of Egypt, and a pillar to the LORD at its border.  It will be a sign and a witness to the LORD of hosts in the land of Egypt. When they cry to the LORD because of oppressors, he will send them a savior and defender, and deliver them.  And the LORD will make himself known to the Egyptians, and the Egyptians will know the LORD in that day and worship with sacrifice and offering, and they will make vows to the LORD and perform them.  And the LORD will strike Egypt, striking and healing, and they will return to the LORD, and he will listen to their pleas for mercy and heal them.
 In that day there will be a highway from Egypt to Assyria, and Assyria will come into Egypt, and Egypt into Assyria, and the Egyptians will worship with the Assyrians.
 In that day Israel will be the third with Egypt and Assyria, a blessing in the midst of the earth,  whom the LORD of hosts has blessed, saying, “Blessed be Egypt my people, and Assyria the work of my hands, and Israel my inheritance.”
You just can’t grasp how crazy it was for Isaiah to tell Israel this message from God. It’s no surprise that [SPOILER ALERT] he was eventually killed by a king by being sawed in two.
Egypt: the nation that dealt unjustly with Joseph. They imprisoned the Hebrews for 400 years and became a symbol of the life of sin and slavery for over 2000 years running at this point.
Not only is Isaiah saying that there will be people that follow YHWH in Egypt, but that they will have an altar set up on the highway to show it! They are going to have the equivalent of a neon sign like “Welcome to Las Vegas” set up for people to worship God in Egypt.
If there were ever a trifecta of enemies in ancient history, it would be Egypt, Israel, and Assyria. Israel was wedged in the middle of those enemies, and when Israel had an evil king, it would run from one of those countries to another for protection from the other one. It was a mess.
But God is so great in His power and in His mercy that one day He will rule all three.
This points to all of the enemies that the people of God would ever have. Even in those places, where people are as against God as anyone could be, there are people seeking Him.
God promises to bring His church, His body, together one day. His people, the work of His hands, and His inheritance are all one people, regardless of their country or their race.
Isaiah saw the day when they would come together, and it would be the Lord’s great work and a sign of His great work all at the same time.