According to Genesis, God placed a rainbow in the clouds as the sign of the covenant after Noah's flood.
Genesis 9 presents the covenant between God, Noah, his descendants, and every living creature. The rainbow serves as a reminder that the waters would not again become a flood destroying all life. It is therefore more than a weather detail: within the story, it is a visible sign of a promise.
The rainbow is sometimes confused with the olive leaf brought back by the dove. Those are separate moments. The dove's leaf signals that land is reappearing, while the rainbow appears later during the covenant scene. In Jewish and Christian interpretation, the passage is also associated with the Noahide covenant, a universal promise extending beyond Noah's immediate family.