We are not told how long it took Noah and his sons to build the ark. Yet we could reason that it was arguably 100 years at most and probably less. We can make this argument because we are told that when he was 500 years old, Noah began to have his three sons (Genesis 5:32). Presumably Noah did not use child labour and so if he built with all three of his sons then they may not have begun until the youngest was, say 20 years old, and the ark would have been 80 years in the making. Another line of argument is that when God told Noah that His Spirit would not strive with man forever, yet his days shall be 120 years (Genesis 6:3), God was speaking of mankind and He had started His stop watch to the time of the Flood. Now that may have been long before He began to explain to Noah about what He planned to do and told Noah to get an ark ready.
At the end of chapter 6 the last verse declares that “Noah did everything just as God had commanded him.” That ‘everything’ was to get the wood and build an ark according to God’s design; get all the food ready for the various animals and then get all the animals on board. Into the ark came seven pairs of each clean animal and only one pair of each unclean animal. When the ark was completed and Noah and his family and all the animals had entered, the Lord personally shut the door (Genesis 7:16). It was a very significant act. Not since the Fall had God personally intervened on earth.
Once the door was shut the rains fell for 40 days and nights, then, for 150 days the waters flooded the earth. During that period every living creature on earth, under then entire sky, died. God’s judgment against sin is total. His ability to save the righteous in the midst of such great destruction is without doubt.
Dear Lord, I am humbled that You didn’t get angry and destroy the earth before You made a plan to rescue the righteous. O God, may I be found righteous in Your eyes at this time when You are once again angry with this world because of our great sin. May I and my family be rescued from the wrath that is to come (Luke 21:36).