God set a rainbow as the sign of the covenant after the Noah’s Ark Flood, according to Genesis 9. The covenant promises that a flood will not again destroy all life on earth in the same way, and the rainbow serves as its visible reminder.
In the narrative, Noah leaves the ark and builds an altar. God then establishes the covenant not only with Noah and his descendants but also with living creatures. The rainbow is described as appearing in the clouds and as a reminder of that promise.
The rainbow’s biblical role is distinct from later uses of rainbow imagery in art, religion, and modern social movements. In Genesis, its purpose is specifically connected to the post-flood covenant and divine remembrance.
The passage does not say that rainbows first appeared only after the flood. Instead, it presents the rainbow as a sign assigned a new covenant meaning. This distinction helps avoid reading the story as a scientific explanation of how rainbows form.