Genesis 6

2 Some people think that these could have been angels or demons that were able to take the shape of men. However, this phrase could just as easily refer to human men.
3 Up to this point, men were living to extremely long ages. At this point God limits the human life span to 120 years. When one looks at a graph of life spans, it is interesting to see how this came true. After the flood, life spans dropped off dramatically. Average life span is around 70 now, but only a small number of people have even approached the 120-year age limit in recent memory.

Some also take this as a prophecy of the Flood. One hundred twenty years from this point, God would flood the earth. See the commentary on Gen 7:6 for more details.

4 There was a lot more variation in the human genome than we see now. A few giants are recorded in scripture.
5 Over the course of time, parents failed to tell their children about God. Thus, people either did not know of God, or refused to live by His standards. When people decide to live by their own standards, they become very displeasing to God. Human standards are not only lower than God's are, but they tend to degenerate with time.
6 This grief was probably similar to ours when we have a close friend turn on us. God created people to have a relationship with Him, but each one turned away from Him.

This is not an admission that God made a mistake in creating people. God was not "surprised" by what happened because He is omniscient. He knew this was going to happen, but that did not do much to ease the pain.

7 God loved people, but His purity and goodness could not allow such corruption to continue. Sin had corrupted the entire earth, and the only way to purify it was to destroy it. People were so thoroughly corrupted that there was not hope of turning them back to God. Their fate was sealed.
8 Nevertheless, one man stood out. Only one man in the entire world loved, respected, and obeyed God.
9 Noah had a relationship with God, similar to the one that Enoch had, and similar to the one Adam had before the Fall. The only way we can please God is to walk with Him.

Noah was a just man. He encouraged others to do what was right. He was also "perfect," meaning that he conducted himself in a right way and never gave in to evil.

10 Shem was born when Noah was 502 years old, and 98 years before the Flood (Gen 11:10).
11 Violence was so widespread that even the soil was corrupted in God's site (undoubtedly due to bloodshed). This may also indicate that the animal world was corrupted and violent as well.
12 This verse speaks of the global nature of the corruption.
13 Noah was God's friend, so He confided in Noah and told him of His plans. The earth would be destroyed, but Noah was to be spared.

God has graciously postponed destruction of the earth until the Last Day because He foreknew that some of Noah's descendants would come to know Him. While the earth is mostly corrupt and wicked today, many people love and know God.

14 We do not know what gopher wood was.

Some have mistakenly thought that pitch was the same thick petroleum substance we get today when we process crude oil into products such as gasoline and motor oil. The oil deposits we harvest from today are best explained as remnants of the Flood, and would not have been available before the flood.

Instead, pitch was most likely a plant substance. It may have been a natural resin or may have been cooked or pyrolized into a pitch-like substance.

15 God now gives detailed instructions about the large craft that Noah was to build.

It is not said whether people knew what boats were before this time. There was only one continent, and there may have been no need to travel by water. It is also not known if Noah was near a body of water when he built this giant boat. In any event, there was no craft like it, and it certainly would arouse the interest of anyone who heard about it. Alas, none turned away from their wicked deeds, as will be seen later.

The design of the ark made it very stable. Those who have tested models of the ark have found that it was self-righting in under extreme simulated conditions. The ferocity of the Flood would require that the survivors had such a boat.

The ark was box-like and was intended to float, not sail. The six to one ratio of length to width is still used by boat builders today.

16 The most common models have this window running the entire length of the ark. This is the only ventilation feature spoken of for the ark. A single door provided for the loading and unloading of the craft. Three decks would be needed to house the animals and store the food (and perhaps drinking water) for the yearlong wait in the ark.
17 The global corruption would be wiped out with a global Flood. Those who consider the Flood to have been only a local event should consider the global language used throughout this account. In addition, if the Flood were only a local event, there would be no need for an ark. God could have simply told Noah to migrate to another place.
18 The covenant or promise was twofold: be fruitful and multiply, and a Seed would crush the serpent's head. These promises were to be bestowed on Noah's descendents.
19 Many people have questioned whether all the animals could have fit on the ark. Several authors have shown that it is possible.
20 Noah did not have to hunt the world; the animals would migrate to him. The ark was under construction for many years, so the animals, insects, etc. would have time to get there.

Plants were not taken. Many plants would survive either on the ark (e.g., the grains used as food), as seeds, or as floating fragments (or even mats). No land creatures would survive the Flood, except those on the ark.

21 Food for all the people and animals was needed for an entire year. Noah either grew and harvested the food himself, or gathered it from the surrounding area (probably a combination of these).

Some have suggested that hibernation might have been used by God to reduce the food requirements for the animals and the workload for the people.

22 Noah obeyed the commands, although they might have seemed strange and impossible.