In the Noah's Ark account in Genesis, a rainbow marks God's covenant with Noah.
After the flood, Genesis 9 describes God establishing a covenant with Noah, his descendants, and every living creature. The rainbow is presented as the sign of that covenant. Its appearance recalls the promise that the waters would not again become a flood destroying all life on Earth.
The rainbow is distinct from the dove and its olive leaf. The dove is a narrative sign that the floodwaters were receding, while the rainbow appears later as a covenant symbol. Biblical translations sometimes use “bow” or “rainbow”; in context, the sign is conventionally understood as the visible rainbow in the clouds.