Genesis 9:7

And you, be ye fruitful, and multiply; bring forth abundantly in the earth, and multiply therein.

The record of Genesis to which this command belongs is divinely inspired. Noah was a real, historical person, and the Flood was a real, historical event. That certainty is established by Christ's own references to Noah and to the Flood.

After the Flood, humanity was commanded to grow in number and to spread abroad throughout the earth. That charge renewed the commission first given to Adam, that mankind should replenish the earth and subdue it.