John Calvin on Isaiah 43:17

17. When he bringeth out. He shows that no power or forces shall hinder him from delivering his people, whenever he shall think proper. The sea which lay between them could not prevent God from “bringing out” his people; but he divided its waters in the midst, and drowned the pursuing enemies, with their horses and chariots. (Exodus 14:28.) This is therefore an amplification; as if he had said, “Though the whole world be leagued for your destruction, and attempt, to hinder the deliverance of my Church, yet it will gain nothing; for not only will the Lord find out a way through whirlpools, when he thinks proper, but he will overthrow and scatter all opposing efforts, and will crush them so that they shall never again raise their head.”

They are quenched like flax. It is possible that he who was vanquished in one battle may renew his strength in another, and at length be victorious; but here the Lord promises a continual victory, for he declares that the enemies shall be subdued in such a manner that they shall be completely extinguished. By the metaphor of flax, he expresses more vividly the sudden destruction of the enemies; for flax may indeed burn and give light, but is immediately consumed.