The rainbow was the sign God gave Noah for the covenant never again to destroy the earth with a flood.
In Genesis 9, God establishes a covenant with Noah, his descendants, and every living creature after the Flood. God says that the rainbow in the clouds will serve as a sign of this covenant. Whenever the rainbow appears, the text presents it as a reminder of the promise.
The covenant is broader than Noah’s immediate household. Genesis includes future generations and the animals that survived the Flood, making the sign part of a relationship between God, humanity, and the living world. The promise concerns destruction by floodwaters specifically; it does not say that no other disasters can ever occur.
The rainbow has consequently become one of the most recognizable symbols associated with Noah’s Ark. In biblical language, the sign is connected to remembrance: seeing it recalls the promise. Other famous biblical signs, such as the burning bush and the pillar of fire, belong to different stories and are not part of Noah’s covenant.