Just like its spiritual father, Satan, mankind uses God's beautiful creation self-centeredly and destroys.
In Genesis 1-3, we see God graciously giving mankind wonderful gifts to enjoy life. He provided them with long lives and brilliant minds to make use of earth's resources. In Genesis 6, though, we see humanity destroying virtually every good gift in its savage disrespect for Him and what He had made. An ever-increasing population was living nearly without restraint. Perhaps the most astounding detail in this whole mess is what all this did to God: He was grieved in His heart that He had created humanity.
To appreciate the Flood and the covenant that resulted, we need to grasp a major factor that directly led to it. God does not judge impatiently or carelessly; He is merciful and gracious, His actions always motivated by love. Everything He does is in the best interest of His purpose and with the well-being of others at heart. Even considering those two factors, what God did in using an overwhelming Flood to wipe out the entire human population in a matter of a few days is sobering. Undoubtedly, God had good cause.
We have no figures at hand to show how many lives perished, but in 1,600-plus years, combined with their brilliant minds and long lives, not only the population could have been abundant, but the development of the earth's material resources may also have been extensive and advanced. We look forward to having those details revealed in the resurrection.
These considerations indicate that two factors made Him decide to destroy nearly all life and begin all over again: 1) a profound change in the quality of life combined with 2) what was developing in people's minds. God did not have an attitude of defeat or failure. Instead, He primarily considered the result of what was occurring in people's minds. It was a sobering judgment but not nearly as bad as what would have been produced had He allowed events to continue. His judgment provides us a clear understanding of His loving character.
God's reaction was guided by what He saw regarding mankind's sins. In His experience with humanity at this point, He concluded that sin should not be understood as a mere imperfection in character but as a hostile, infecting, poisonous, and destructive force relentlessly driving people to even greater excesses. Added to this reality is an element that significantly raises the level of seriousness: Sin is not merely murder, lying, coveting, thievery, etc., but a vicious motivation buried deeply in men's hearts that generates evil almost incessantly.
God's statement that “every intent of the thoughts of his heart was only evil continually” is not an exaggeration. The heart is a generator of evil by nature (Matthew 15:16-20). In Ecclesiastes 7:29, Solomon reminds us, “Truly, this only I have found: That God made man upright, but they have sought out many schemes.” How far mankind had fallen from the pinnacle of purity and righteousness Adam and Eve contained when created by this same God! How radically that beautiful creation had changed!
Sin, then, is not merely what one sees on the outside. Far more challenging to understand and deal with is the reality that it is an internal matter; sin is generated from within. This is all the more interesting because Jesus later admonishes us not to look on the outward appearance in making judgments (John 7:24). Yet, we must do this because we lack the godly powers to judge as God does.
I Samuel 16:7 says that in His judgments God looks on the heart. From this incident, the wisest of all Beings, God Himself, teaches us a valuable principle of judgment: When the heart becomes so consistently wicked that evil is its natural course of action, nothing can be done to change it.