Genesis 6:2  “…sons of God saw the daughters of men…took wives for themselves of all whom they chose”
Questions have arisen over who were the sons of God and the daughters of men.  Here and in verse four.  But from what we’ve read thus far, this seems to be a reference to the line of Seth which followed God and all the other lines which apparently did not.  I get the feeling this is going to be a problem similar to that the Israelites had to deal with a lot, intermarriage with a people that didn’t follow God.  The foreign wives would turn the hearts of the men to other gods.  Happened to Samson and Solomon, which is why God eventually told them not to do it.

3  “…My Spirit shall not strive with man forever…”
I’ve heard this used for years to say that God won’t continue to call someone to be saved if they keep rejecting Him, that there is a point after which God will stop calling.  I think that is taking this verse out of context.  The text here is referring to how man has become so corrupt at this point in history, and God has decided He’s not going to put up with him much longer.  Personally, while I know that God can do whatever He wants and be totally justified with any action, I think that as long as a person is breathing there is hope that he can come to Christ.  A person’s heart may get so hard that it is improbable that he would accept Christ, but that would be on him and not on God.

3  “…his days shall be one hundred and twenty years”
As with the previous phrase in this verse, I think some have taken this part out of context as well.  I’ve heard this is the reason mankind stopped living so long, that God limited his lifespan to one hundred and twenty years.  Problem with that is man did and has recently lived longer than one hundred and twenty.  I think God was saying man’s time on the planet at that point was one hundred and twenty years before He destroyed all of them.  Previous chapter said Noah was five hundred years old when he had his sons, and we’ll find that he was six hundred years old when the flood began.  Since we’re not given a specific timeline by years, it’s not hard to assume one hundred and twenty years from the time God said this until man is destroyed by the flood.  We’re also told by Peter in his writing that Noah was a preacher to those of his day while he was building the ark.  God gave the people of that day time to repent of their sin, to escape the coming destruction, but they chose otherwise.  Much like today, unfortunately.
Reminds me of what Christ said about the last days being like the days of Noah.  We focus on several aspects of comparison, but the greatest is that men will choose their sin over repentance, even knowing the destruction to come.

4  “…giants on the earth…mighty men who were of old, men of renown”
Have heard many strange interpretations of this section, including aliens and angels mating with mankind.  If we stay within the context of verse three, it becomes more of a comment on the type of men that existed then and compares them to men who would come later.  The same thing would happen again in the land of Canaan before the Israelites arrived.  Actually, if we go back and look at all four verses, it appears to set up what God is about to do because of mankind.  When men began to grow in number, it reached a point where those who followed God began to intermarry with the ungodly, a sign of the majority of mankind beginning to fall away from God.  At this time, there were men who acted more and more out of their wickedness.  Similar to the idea of Lamech of the line of Cain who had two wives and boasted of how he killed someone for wounding him.  Evil men are never content with their evil, they must continually push the boundaries.  Commentary has similar idea.  Suggests the terms giant, mighty men, and men of renown as used here refer more to their actions and behavior as the ungodly rather than their physical stature, of “reckless ferocity, impious and daring characters.”

Recap might be helpful:
1  “…when men began to multiply…” – as the population of mankind began to increase.
2  “…sons of God saw the daughters of men…took wives for themselves…” – the Godly began to intermarry with the ungodly showing that mankind was leaving Godliness and becoming evil continually.
3  “…My Spirit shall not strive with man forever…his days shall be one hundred and twenty years” – God’s patience with mankind’s wickedness has ended.  He is going to give man one hundred and twenty years to repent before He destroys him.
4  “…giants on the earth in those days…also afterward…when the sons…mighty men…men of renown” – evil men doing very evil things.  Phrase when the sons of God and following are pointing to that time in history and comparing it to the time referred to by the phrase also afterward.  Similar instance of evil men arising during a time of intermarriage occurs in the land of Canaan when the Israelites arrive.

5  “…every intent of the thoughts of his heart was only evil continually”
Idea which has just been conveyed.

7  “…I am sorry that I have made them”
The saddest commentary.  To have Almighty God, the one who’s patience is beyond measure, say He is sorry He has made mankind.

8  “…Noah found grace…”
God always has His remnant.

12  “…God looked upon the earth, and indeed it was corrupt; for all flesh had corrupted their way on the earth.”
For all his intelligence and good intentions, mankind left to himself will corrupt his way and destroy himself.  He cannot evolve into a better version of himself as long as his sin nature is present.  Man has no way to remove that nature apart from God.

13-22  Announcement of the coming flood and instructions on building the ark.  Some have denied the idea of the ark based on the suggestion that Noah wouldn’t have the knowledge to build it.  It has already been mentioned that man learned quickly in his acquisition of skills, especially since he lived so long and could pass on knowledge directly.
While Noah may have had knowledge of shipbuilding, the ark isn’t a typical ship.  It was built more as a floating container, designed to withstand the watery upheaval that God was about to unleash.  Accounts for God’s specific instructions.
Some have wondered at the size of the ark, could it hold two of every land animal.  Due to the short time period since creation, the different varieties of each species may not have existed as yet.  It states to bring two of every sort.  Those would have the necessary genetic makeup to reproduce the species over time.  The same thing can be said of Noah and his sons.  All people groups can trace their ancestry back to him.  Mankind is divided into families or people groups, not races.  There is only one race on the planet, the human race.

20  “…two of every kind will come to you…”
Noah didn’t have to chase and capture the animals, they came to him.

I hope you enjoy reading and studying His word.  May it accomplish what He desires.  Please feel free to comment or post questions.  Thanks for reading!

Scripture taken from the New King James Version®. Copyright © 1982 by Thomas Nelson. Used by permission. All rights reserved.