According to Genesis, God placed a rainbow in the cloud as the sign of the covenant after the Flood.
Genesis 9:12–16 describes God’s covenant with Noah, his descendants, and every living creature. God says that the rainbow in the cloud will serve as a reminder of this covenant and the promise that waters will not again become a flood destroying all life. The sign therefore follows the Flood narrative and extends beyond Noah’s immediate family.
The rainbow is presented as a visible sign associated with clouds and rain. In the biblical story, its meaning is theological and covenantal rather than an explanation of how light is physically dispersed. The passage repeatedly connects the rainbow with remembering the promise.
Some retellings call the sign a rainbow bridge or a colored arc, but Genesis specifically uses the rainbow image. It also describes the covenant as involving the earth and living creatures, not only Noah. That broader scope is an important part of the passage’s meaning.