In the biblical Noah's Ark story, God set a rainbow as the sign of the covenant after the Flood.
Genesis 9 describes a covenant between God and Noah, his descendants, and every living creature. God promises that a flood will not again destroy all life on earth, and the rainbow in the clouds is given as the visible sign of that promise.
The covenant is presented as universal in scope. It is not limited only to Noah's family; the text explicitly includes animals and the earth. This makes the rainbow one of the most recognizable symbols associated with the Flood narrative.
The rainbow appears after Noah leaves the Ark and builds an altar. It should not be confused with the olive leaf brought by the dove, which signals that the waters had receded. The dove's leaf and the rainbow are separate symbols in the account.