In Noah’s Ark, Genesis uses a rainbow as the sign of God’s covenant after the Flood.
After Noah leaves the Ark, Genesis 9 describes a covenant between God, Noah, his descendants, and every living creature. The rainbow in the clouds is presented as the visible sign of that promise. The covenant states that a flood will not again destroy all flesh and the Earth.
The passage is not merely a weather observation. It gives the rainbow a theological meaning within the story: it serves as a reminder of the covenant. The promise is addressed broadly, including animals as well as humans, which gives the episode a universal scope.
An olive leaf belongs to an earlier scene, when a dove returns to the Ark and shows that the waters are receding. The dove itself is also a separate symbol in later art and religious tradition. For the covenant sign specifically, however, Genesis identifies the rainbow.