the people which I formed for myself, that they might declare my praise.
God is described by what He did at the Red Sea, but now commands: forget the old things. He works something new. The road through desert and streams through waste places typify redemption from Babylon as the Egyptian deliverance typified it. The creatures praise Him because He supplies water where none existed.
AI summary
Commenting on Isaiah 43:16-21
This people--namely, The same as "My people, My chosen" (see Isa 43:1, Isa 43:7; Psa 102:18). my praise--on account of the many and great benefits conferred on them, especially their restoration.
But thou hast not called upon me, O Jacob,.... The Jews, though they were the posterity of Jacob, a praying person, yet did not tread in his steps, but were more like the Heathens that called not on the name of the Lord; though there is no necessity of restraining this to prayer, it may regard the whole worship of God, which is sometimes included...