When the world was filled with wickedness, God decided to cleanse the earth with a great flood. Noah, a righteous man, found favor with God. God instructed him to build an ark to save his family and pairs of every animal. After forty days and nights of rain, the waters covered the earth, but Noah and his family were safe. When the waters receded, God made a covenant with Noah, promising never again to destroy the earth with a flood, and He set a rainbow in the sky as a sign.

"I have set my rainbow in the clouds, and it will be the sign of the covenant between me and the earth."

Genesis 9:13