‘In that day there will be an altar to Yahweh in the midst of the land of Egypt, and a pillar at its border to Yahweh, and it will be a sign and a witness to Yahweh of hosts in the land of Egypt. For they will cry to Yahweh because of the oppressors, and he will send them a deliverer and a defender, and he will deliver them.'
These are further evidence of their total conversion to Yahweh, again in terms of the symbols of the day. The setting up of an altar was a token of submission to the god for whom the altar was set up, in this case the living God (compare Joshua 22:34), and its being in the midst declared that it was for all Egypt. It would be conceived of as a memorial altar for no other altar would be conceivable to Israel outside God's land. The setting up of a pillar on the border would be a sign to all who entered of the presence of God there (Genesis 28:18). Thus they would be a sign and a witness to Yahweh of hosts for the whole of Egypt. And that is what the church of Christ in Egypt became.
But the altar that would be set up is the cross, and the sacrifice that will be offered is our Lord Jesus Christ (Hebrews 13:10; Hebrews 9:26-28; Hebrews 10:12-14). For He is the one sacrifice for sin for ever, after Whose offering no further sacrifice is required.
‘For they will cry to Yahweh because of the oppressors, and he will send them a deliverer and a defender, and he will deliver them.' Not only will Egypt receive the word of Yahweh, but they will receive a Deliverer, a Saviour. And He will bring them deliverance far more wonderful than Isaiah could ever know. For he will deliver them from themselves, and from sin and from the evils of the world and from Satan. This reference to a deliverer could only, in terms of Isaiah's thought, be to Immanuel Who was coming (Isaiah 7:14), the root of Jesse (11., 1-5, 10), the son who was to be miraculously born of a virginal woman (Isaiah 7:14; Isaiah 9:6), the Saviour, the Prince of Peace.
The pictures are idealistic, but even in spite of the failure of the church to be what it should be, and the reversals suffered since the invasion of Islam, nothing will prevent the final triumph of Yahweh in Egypt. For the remnant have continued in Egypt through the centuries (in the Coptic church) and it will be fulfilled in the new heaven and the new earth when all who are there of Egypt will own His sway, and will worship Him. And God will be all in all. And that is what essentially Isaiah is declaring here. That is his vision.