God set a rainbow in the clouds as the sign of the Noahic covenant.
After Noah leaves the ark, Genesis 9 describes a covenant between God, Noah, his descendants, and every living creature. God promises that a flood will not again destroy all life on earth, and identifies the rainbow in the clouds as the sign of that covenant.
The passage presents the rainbow as a visible reminder of the promise. It is not described as something created for the first time after the flood; rather, the text explains its covenant meaning within the story. The covenant is unusually broad because it includes animals as well as human beings.
The rainbow’s later cultural meanings are extensive. It appears in religious art, literature, and modern symbols of peace and inclusion. In Genesis 9, however, its specific narrative function is to mark the promise that the waters will never again become a flood destroying all flesh.