In Genesis, Chapter 6, we read about the Nephilim and the cohabitation with women and their notorious offspring. In the middle of that discussion we find verse 3 that says, “Then the LORD said, My Spirit shall not abide in man forever, for he is flesh: his days shall be 120 years.” Some translations will interpret 
that phrase for you. The New Living Translation says, “Then the LORD said, My Spirit will not put up with humans for such a long time, for they are only mortal flesh. In the future, their normal lifespan will be no more than 120 years.”
Since the discussion regarding the Nephilim and their lives of sex and violence serve as the primary introduction to the flood, many commentators take the “120 years” reference as referring to the time God gives the world to repent of their violence and rebellion before He destroys them. There are several things that support this interpretation. First, the time of 120 years matches the time it took Noah to build the ark, during which as Hebrews 11 and both Peter’s epistles imply that it was at Noah’s flood that God’s patience ran out and during which Noah preached righteousness as he was preparing the Ark. Second, the lifespan of those following the flood went anywhere from 148 to 600 years. Admittedly, one might suggest that the limitation to the years of man’s life is a general average, not a specific number. Moses himself lived to be exactly 120 years, but Moses suggested in Psalm 90 that man’s lifespan was closer to 70 years, 80 if he be strong, rather than 120. Furthermore, according to Matthews, “Jewish tradition understood the 120 years as opportunity for repentance” rather than the limiting of man’s life span. A final support for the reference to 120 years being a period of grace in which sinful man could repent before the flood is the fact that many early church fathers took the passage this way.
The New Testament writers compare our days with the days of Noah. Peter tells us in 2 Peter 3:9 “The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance.” God so loved the world that he sent His son, the Ark in which man can find refuge from the coming destruction. Verse 10 goes on to say, “But the day of the Lord will come like a thief, and then the heavens will pass away with a roar, and the heavenly bodies will be burned up and dissolved, and the earth and the works that are done on it will be exposed.”
Chuck
“Since all these things are thus to be dissolved, what sort of people ought you to be in lives of holiness and godliness…” 2 Peter 3:11