In Genesis, God set a rainbow in the cloud as the sign of the covenant with Noah.
Genesis 9:12–17 describes the covenant after the Flood and identifies the rainbow as its sign. The covenant extends beyond Noah to his descendants and to every living creature, making it broader than a private promise to one family.
The passage says that when the rainbow appears in the cloud, God will remember the everlasting covenant concerning the earth and its living creatures. In the narrative, the rainbow therefore functions as a visible reminder of the promise that a flood would not again destroy all flesh.
The Genesis text does not describe the rainbow as the cause of the weather or as a magical object. It presents it as a sign within a theological covenant story. Later religious art and popular culture have made the rainbow a widely recognized symbol of hope and peace.