In Genesis, God sets a rainbow in the cloud as the sign of the covenant after the Flood. Genesis 9:13 describes the rainbow as the visible sign of the covenant between God, Noah, and every living creature.
The covenant follows Noah’s exit from the Ark and the establishment of a new post-Flood order. In the passage, the rainbow serves as a reminder of God’s promise never again to destroy all life with a flood. The covenant is presented as extending beyond Noah’s family to all living creatures associated with the earth.
The rainbow’s scientific explanation is different from its theological role in the story. A rainbow is an optical phenomenon produced when sunlight interacts with water droplets, creating the familiar arc of separated colors. Genesis uses the visible phenomenon symbolically as a covenant sign.
The passage does not say that rainbows first existed after the Flood. Its focus is the meaning assigned to the rainbow as a reminder of the promise. Later religious and artistic traditions often treat it as the defining emblem of the Ark narrative.