Original Text
And He sware by His great name: 'Henceforth I will not do so to all who dwell on the earth, and I will set a sign in the heaven: and this shall be a pledge of good faith between Me and them for ever, so long as heaven is above the earth. And this is in accordance with My command.' LV. 3-LVI.
Simple English
He made a solemn promise by His great name: "From now on, I will not do this to everyone living on earth. I will place a sign in the sky, and this will be a promise of good faith between Me and them forever, as long as heaven exists above the earth. This is according to My command."