This post is an overview of Genesis 8:21. To read about the first portion of Genesis 8:21 in greater detail click here, for the second portion click here, and for the third portion click here.
The flood was over, Noah had left the ark, and the aroma of his offering drifted up into the heavens. It is at this point, by the inspiration of the Holy Spirit (and through Moses), that Genesis records what God said in His heart:
The LORD smelled the soothing aroma; and the LORD said to Himself, “I will never again curse the ground on account of man, for the intent of man’s heart is evil from his youth; and I will never again destroy every living thing, as I have done. (Genesis 8:21)The underlying theme in Genesis 8:21 is this: God demonstrating His mercy to man.
Man is fallen. He has a heart that desires evil from youth. Because of sin, man deserves nothing but the wrath of God. Man does not deserve God's mercy. Any mercy that man does receive is a gracious gift.
God shows different kinds of grace towards fallen men. To all men, God shows His "common grace". This "common grace" is described in Genesis 8:21. God gives to all men (without distinction) the promise that He will not add to the curse on the ground (Genesis 8:21).
Jesus also spoke of God's common grace towards fallen man:
He causes His sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. (Matthew 5:45)Even though man is undeserving, God continues to uphold the ecosystem of the earth. Man does not deserve the sunlight and rain with which grow the crops that he does not deserve to eat.
God is the one who chose to be more merciful towards this current era that we live in: the post-flood world. It is God who chooses to restrain His wrath in this current era, choosing not to demonstrate His anger towards sin with another global flood (Genesis 9:11).
It must be noted that the common grace God gives to man cannot save a man. Only saving grace can save a man. It is only through God's saving grace— it is only through His special revelation— it is only through Him changing a man's heart from a heart of stone into a heart of flesh— it is only through the blood of Jesus Christ that a man can be restored to his Creator.