When God created Adam from the dust of the earth, He gave him several commands: tend the garden, keep the garden, and stay away from that tree.
He also gave him another command: Be fruitful and multiply (Genesis 1:28).
To be fair, God also told the birds the same thing (Genesis 1:22). But later on in Genesis, God repeated this exact same command to Noah (Genesis 9:1) and Ishmael (Genesis 17:20).
Now, God says it to Jacob (Genesis 35:11). After that, the command virtually disappears. The words only appear in conjunction a handful of other times, and never to a specific individual ever again.
Why does God keep telling people that? Is He worried that people will all of a sudden cease to be?
Not likely. Instead, these words really only appear when there is a huge void that needs to be fulfilled.
After the creation, there was literally an entire earth that needed to be filled. The same could be said after the flood. Now, with Jacob, it wasn’t a literal earth that needed bodies, but a nation designated for God.
The blessing was not intended to be some kind of pithy comment about reproduction, but a command to continually increase. To grow. To prosper. To develop.
You could argue that Jesus gave a similar command when talking about the church. In Matthew 28:20, Jesus tells the disciples to “go into the world” and make disciples from every nation on earth. The Kingdom is tiny at that point; Jesus is telling them to go fill it.
But God doesn’t just want bodies in pews — He wants souls in the Kingdom. He doesn’t want a membership roll that’s filled with names, He wants the Lamb’s book of life that is covered from cover to cover with names of people who are in His spiritual family.
In that sense, our command is the same as Jacob’s: Go forth and multiply!