What does Genesis 9:5 mean?
Genesis 9 opens with God's blessings and commands to humanity as the world resets following the flood. In the previous verse, God commanded humans not to eat the blood of animals, calling the blood the creature's "life." This is one of the first moments in Scripture where blood, specifically, is tied to life. Later, through moments such as the first Passover (Exodus 12:1–7), and the sacrifices in the temple (Exodus 29:19–21; Leviticus 4:1–21), this reverence for blood will be magnified. The ultimate meaning of this symbol will be fulfilled in the sacrifice of Jesus Christ on the cross (John 1:29; 1 Corinthians 5:7).This verse pivots from an animal's lifeblood to the shedding of the blood of humans. This is a new command for the way human communities should conduct themselves; it is a change from God's requirements for mankind before the flood. Specifically, God will require a reckoning—a dire accountability—when the lifeblood of a person is shed. God will require that reckoning whether the one who kills a person is a man or an animal. The next verse will reveal that reckoning to be the death of the one who kills any human being.
Following the first recorded murder in Scripture, God allowed Cain to live and, in fact, to thrive on the earth. With this new beginning after the flood, however, God will require death for the intentional, unjustified killing of another person.