Jamieson, Fausset and Brown on Isaiah 43:25

25. I, even I--the God against whom your sin is committed, and who alone can and will pardon. (Is 44:22).

for mine own sake--(Is 48:9, 11). How abominable a thing sin is, since it is against such a God of grace! "Blotted out" is an image from an account-book, in which, when a debt is paid, the charge is cancelled or blotted out.

not remember ... sins--(Jr 31:34). When God forgives, He forgets; that is, treats the sinner as if He had forgotten his sins.