What does Genesis 7:23 mean?
These last few verses of chapter 7 seem repetitive, and they are. This is a very deliberate technique, used often in ancient literature. Stating certain facts over and over was a way of emphasizing their truth and importance. In this case, Genesis is making it clear that no human or animal life survived the flood, other than those aboard the ark.This verse also uses repetition to remind us that this wasn't "just" a natural catastrophe. God blotted out (or wiped out) all the human and animal life. He caused the flood. As Creator and Judge and God, He acted out of His authority to execute justice. In a sense, God is un-making some of what He has made, by taking dry land back beneath the water (Genesis 1:9–10). God would not allow the violence of mankind to go on as it had. He ended it.
From this distance, and from a merely human perspective, this scale of death is inconceivable to most of us. It is uncomfortable. It challenges our very idea of who our God is. It is essential that we understand both His righteousness and His mercy. God has not changed in His nature. He will not abide sin, and He will in mercy save some from destruction.
The rest of the Bible is the story of how sinful, mortal man could ever possibly be at peace and even loved by such a righteous, powerful, just, and holy God.