In the Genesis account of Noah’s Ark, a rainbow marked God’s covenant after the Flood. Genesis 9 presents the rainbow as the sign of a covenant between God, Noah, his descendants, and every living creature.
The covenant includes a promise that the waters would not again become a flood destroying all life on earth. The rainbow therefore serves as a visible reminder of the promise within the story, rather than merely as a description of weather after a storm.
Genesis 9:13–16 is the passage most directly associated with this sign. The rainbow is also used in later Jewish and Christian art as a symbol of hope, mercy, and renewed relationship. The text specifically identifies a rainbow, not a rainbow-colored object, a star, or an eclipse.