What does Genesis 6:17 mean?

In prior verses, God has told Noah that He would put an end to all the people on the earth. This is due to their violence and evil (Genesis 6:5; Genesis 6:13). After making this grave announcement, God gives Noah instructions about how to build an ark (Genesis 6:14–16). Those directions included the materials Noah should use, the dimensions of the ark, and the features it needed to have.

This verse, now, is actually the first time that God reveals how He will destroy all life. God will bring a killing flood to wipe out everything that breathes. All land-dwelling life will die. In some sense, this is God taking His creation back to a very literal "reset." In the beginning, God transformed the earth by bringing land and animals out of the water. In the flood, He will send the earth, at least symbolically, back into the state it was in prior to man's creation.

This must have been overwhelming for Noah to hear. God is going to judge mankind by destroying almost all people. That judgment will wreak havoc on the animals and the land, as well. Beyond that, only Noah and his family will survive, and only by constructing a massive ark. Indeed, it's overwhelming for us to consider, all of these millennia later. God is planning to exercise His authority as Creator and Lord of all the universe by delivering justice against human sinfulness and violence. As the following verses will reveal, God will also demonstrate His grace by saving one human family and two of every animal so that created life will continue.