In Genesis, a rainbow became the sign of God’s covenant after Noah’s Flood.
Genesis 9 presents the covenant made with Noah, his descendants, and every living creature after the waters recede. God says that the rainbow in the clouds will serve as the sign of this covenant and recalls the promise never again to destroy all life by a flood.
The covenant is broader than a private promise to Noah. Its stated scope includes future generations and the animals that survived the Flood. The rainbow functions as a visible reminder whenever clouds appear and the covenant is remembered.
The biblical passage does not claim that rainbows first existed after the Flood. Instead, it assigns the natural phenomenon a new covenant meaning within the story. The rainbow is therefore distinct from the dove’s olive leaf, which signals the return of vegetation.