John Calvin Commentary Genesis 9:7

"And you, be ye fruitful, and multiply; Bring forth abundantly in the earth, and multiply therein." — Genesis 9:7 (ASV)

And you, be ye fruitful and multiply. He again turns his discourse to Noah and his sons, exhorting them to the propagation of offspring: as if he would say, ‘You see that I am intent on cherishing and preserving mankind; therefore, you also attend to it.’ At the same time, in commending to them the preservation of seed, he deters them from murder, and from unjust acts of violence. Yet his primary purpose was that to which I have previously alluded: that he might encourage their dejected minds. For these words contain not a mere precept, but also a promise.