What does Genesis 6:20 mean?
In the previous verse, God commanded Noah to bring into the ark with him and his family a male/female pair of every kind of animal. Now God expands and clarifies the command. First, the animals will include birds, insects, and every other kind of land-dwelling animal. Second, all of these animals would come to Noah to be kept alive. These creatures would have been necessary to re-populate and replenish the land ravaged by the upcoming flood.With the addition of the detail that the animals would come to him, Noah's impossible task of building the ark and collecting the animals becomes a little less impossible. God would exercise His supernatural authority over the animals to direct specific pairs to come to the ark to be saved from the flood. Noah isn't being asked to scour the earth capturing unwilling animals. He's being asked to prepare an ark for the ones which come to him. That's still daunting, but much more within the abilities of one man.
We see in this command that God's response to the great wickedness of humanity is not simply to destroy all life, but to preserve life, as well, for a new beginning. The flood is not an act of revenge, but of drastic healing.