Exodus themes play a large role in the second part of Isaiah (see Theological Themes). God will bring the chosen people out of Babylon just as surely as God had brought them out of Egypt hundreds of years ago. The exodus imagery is clear in this passage, with its references to the God who makes a way in the sea, who quenches the enemy chariots and warriors like a wick--the God whom Israel had remembered ever after at the annual Feast of the Passover.
But there is a surprise here: Remember the exodus? Now, forget it (v. 18)! Not because the old deliverance was invalid, but because it is about to be surpassed. God never rests on God's past laurels, nor should Israel.
At several places in the latter half of Isaiah, the prophet speaks of "former things" (41:22; 42:9; 43:9, 18; 46:9; 65:17). Though the meaning seems not always to be exactly the same, the sense is always to point to what God is doing now, sometimes surpassing, sometimes replacing what God had done before. In 41:22, the "former things" and the "things to come" seem to refer to doing anything and everything--which God can and does do, while the idols cannot. Occasionally, the "former things" might refer to the times of judgment brought upon Israel by its rebellion, which, now, happily, are past (42:9; compare 40:2)--the old closed hearts and eyes and ears of Isaiah 6:10 are replaced by God's giving sight to the blind and open doors to the captives (42:7).
The present passage (43:16-21) is perhaps the most striking: God is about to outdo the exodus itself, the work that established Israel in the beginning. The poetic play in the passage is delightful as well as theologically inspiring: the old way was a dry way in the sea (v. 16); the new way is a wet way in the desert (v. 19)--so ecologically refreshing that the animals, too, will rejoice (v. 20). Here the prophet, at God's impetus, preaches on the old exodus text to make a point about God's new work. It is like the old and not like the old--an important biblical theme that has here one of its clearest expressions. God will act as God has done in the past, because God remains consistently committed to acts of deliverance; God will do a new thing, because God is always taking people to surprising new places.
Apparently part of God's new thing is a new kind of deliverance. In the old exodus, the horse and rider were thrown into the sea (Exodus 15:1). The Egyptians were quenched like a wick (Isaiah 43:17). But that is precisely what God's gentle servant will not do (42:2-3). Now God will bring Torah and justice to the nations in a new way.
16 Thus says the Lord,
who makes a way in the sea,
a path in the mighty waters,
17 who brings out chariot and horse,
army and warrior;
they lie down, they cannot rise,
they are extinguished, quenched like a wick:
18 Do not remember the former things,
or consider the things of old.
19 I am about to do a new thing;
now it springs forth, do you not perceive it?
I will make a way in the wilderness
and rivers in the desert.
20 The wild animals will honour me,
the jackals and the ostriches;
for I give water in the wilderness,
rivers in the desert,
to give drink to my chosen people,
21 the people whom I formed for myself
so that they might declare my praise.
New Revised Standard Version Bible: Anglicized Edition, copyright © 1989, 1995 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org