Paul reminds these believers again that keeping the law could not save a person and that the law did not add a new condition to the promise by faith given to Abraham.
The word "curse" here is a metonym for God condemning the person whom he has cursed. AT: "from us having God condemn us because we broke the law ... having God condemn him instead of us ... God condemns everyone" (See: [[rc://en/ta/man/translate/figs-metonymy]])