Why was it that God, blessing Noah and his sons, said, "Increase, and multiply, and replenish the earth, and rule over it; and let your fear and the dread of you be upon all beasts, and upon flying fowls, and upon reptiles, and upon the fishes which I have placed under your hand?" (Genesis 9:1).
God Blesses Noah to Increase and Multiply After the Flood
The Midrash of Philo 1:1