John Calvin on Isaiah 43:15

15. I Jehovah. This verse contains no statement, and only shews who it is that speaks, how great is his power and majesty, and, in a word, how warmly he loves the elect people, so as to give greater weight to the former promise. In short, it may be viewed as the seal of the preceding statement, more powerfully confirming what was formerly said, that it is God who makes these promises. But what God?

Your Holy One, the Creator of Israel, your King. He is called Holy, because he has chosen and separated a people, that he might consecrate them to himself; for by this title he reminds them of the adoption by which he united them to himself in a peculiar manner, that they may understand that he will be their Father and Savior. And for the same reason we ought now to acknowledge him as our Holy One, because he has set us apart to be members of the Church, of which we are assured by our calling. The name Creator must not be viewed as referring to universal creation, by which unbelievers also are created, but to the new creation, on account of which we are also called (Ephesians 2:10) “his workmanship,” (τὸ ποίημα) as we have formerly stated, while expounding other passages.

Your King. This might indeed be thought to be absurd; for not even the semblance of a kingdom was visible, and nothing was to be seen among the Jews but what was covered with shame and disgrace, in consequence of their having been deprived of all aid and relief. Yet there was room for the exercise of faith, that they might hope for the restoration of the kingdom, though apparently ruined and almost extinguished, and might acknowledge God to be their King.