Short answer: As a judgment for the wickedness of mankind
Bible Reference: Genesis 6:5-7, 11-13, 17
The Bible records that after Adam and Eve disobeyed God in the Garden of Eden that sin entered into the world, and death by sin. Adam’s firstborn son, Cain, became the world’s first murderer, killing his brother Abel. From there, things simply got worse and worse.
The Bible records on Genesis chapter 6 that:
“GOD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually. And it repented the LORD that he had made man on the earth, and it grieved him at his heart. And the LORD said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.” Genesis 6:5-7
These verses reveal that God sent the Flood as a divine judgment against man’s sin. Mankind had gotten so bad that his every thought and imagination was always pure evil! Furthermore, God notes that the earth was filled with violence because of man. This was a dark time for humanity. Imagine a world where every day was filled with crime, murder, hate, war, theft, extortion and pretty much any other sin man can come up with!
Perhaps a comparison would make things a little clearer. God told Abraham in Genesis 18 that He intended to destroy the cities of Sodom and Gomorrah for their wickedness. Abraham prayed on behalf of those wicked cities, asking whether God would destroy the righteous with the wicked? God promised He would not destroy those cities if He found even 50 righteous men. Abraham knew of Sodom and Gomorrah’s sinful reputation, so he asked God to lower the number… and to make a long story short, God promised that he would spare the city if there were even 10 righteous men to be found. Unfortunately, when God sent two angelic emmisaries to Sodom, only Abraham’s nephew Lot, his wife and daughters were escaped the cities’ destruction by heavenly fire… and Lot’s wife had her heart so set on Sodom that she forfeited her life to look upon it one last time [Genesis 19:26; Luke 17:32-33].
It should be noted that God takes no pleasure in the destruction of the wicked, but He would rather that sinful men would repent of their sin and turn to Him and live [Ezekiel 33:11; 2 Peter 3:9]! Yet sin cannot go unpunished. Every man, woman and child knows this is true when they stop to think about it. Imagine a world where anyone could steal from you, hurt you, or even kill you or those you love… a world where sinful men are free to do as they please without punishment. It’s not a pretty place, is it? Laws are necessary in a sinful world to protect people from crime as much as to punish criminals. A loving and just God must punish sin, but our Creator also provides a remedy for our sin.
The Bible records that Noah found grace in the eyes of the LORD and that God instructed him to build an Ark so that he and his family might be saved. Likewise, God has made a way that we might be saved from the punishment our sin deserves. His only begotten Son Jesus Christ died on a cross for the whole world’s sin, taking our punishment in our place so that we could be forgiven and be restored to right standing with God. Then Jesus rose again from the dead to give us the promise of eternal life. Whoever confesses the Lord Jesus and believes in their heart that God has raised Him from the dead shall be saved.
My you, like Noah, find grace in the sight of God.