What sign did God give Noah as the covenant after the flood?

A rainbow was the sign God gave Noah as the covenant after the flood.

In Genesis 9, God establishes a covenant with Noah, his descendants, and every living creature that survived the flood. The rainbow is placed in the clouds as the sign of that covenant.

The stated purpose of the sign is to recall the promise that the waters would never again become a flood destroying all flesh. The rainbow therefore functions within the story as a visible reminder of divine commitment.

The account also broadens the covenant beyond Noah's family to include animals and the earth. An olive leaf belongs to the earlier episode involving the dove; it is not the covenant sign specified in Genesis 9.