In Genesis, a rainbow marks God’s covenant with Noah after the Flood.
Genesis 9 presents the rainbow as a sign of a covenant between God and Noah, his descendants, and every living creature. The covenant promises that a flood will not again destroy all life on Earth. The rainbow appears in the clouds as a reminder of that promise.
The sign is connected with the post-Flood covenant, not with the earlier olive leaf carried by the dove. The olive leaf shows that vegetation had returned, while the rainbow represents the covenant itself.
Rainbows are optical phenomena produced when sunlight interacts with raindrops through refraction, internal reflection, and dispersion. Genesis uses this familiar atmospheric feature in a theological narrative about remembrance and preservation.