Genesis gives the rainbow as the sign of God’s covenant with Noah after the flood.
In Genesis 9, God establishes a covenant with Noah, his descendants, and every living creature that a flood will not again destroy all life on earth. The rainbow in the clouds serves as the visible reminder of that promise.
The passage places the covenant after Noah leaves the Ark and builds an altar. It is broader than a private agreement with Noah alone: the text repeatedly includes future generations and animals. This universal scope is an important part of the narrative’s closing section.
The rainbow was not invented by the flood story; it is a natural optical phenomenon produced when sunlight is refracted, reflected, and dispersed in water droplets. Genesis gives it theological meaning as a covenant sign. Modern retellings sometimes describe it simply as a promise to Noah, but the biblical wording includes the whole living world.