בראשית ט:יא פירוש: רש״י, ספורנו, אור החיים ורד״ק

והקמתי AND I WILL ESTABLISH — I will give confirmation to my covenant; and in what consists this confirmation? “The sign of the rainbow”, as it goes on explaining at the end.

ולא יהיה עוד מבול לשחת הארץ, there will not ever again be the kind of catastrophe which will destroy the whole surface of the earth at the same time.

והקימותי את בריתי אתכם. And I will keep My covenant with you. We need to understand why the Torah repeated the promise that all flesh would not be destroyed again and that there would not be another deluge. If, as Rava had said in Shavuot 36, the reason is to give this assurance the status of an oath, our sages used both this and the second half of the verse, ולא יהיה המים for that purpose. They ignored 8,21 in that context. I have explained all that in connection with 8,21.