After the ark was finished, at the end of the period of 120 years that God had determined (chapter 6:3), He called Noah and his family to enter the ark because he saw that Noah was righteous before Him in that generation.
Noah was seen to be righteous because of his faith: having been divinely warned of things not yet seen, the circumstances of the flood still to come without any visible evidence or previous experience, he obediently prepared an ark for the saving of his household, as in Hebrews 11:7. It was a giant ark and it took a century to build, because he believed in the LORD, and it was accounted to him for righteousness (Genesis 15:6).
The expression "this generation" represents all of humanity at the time of Noah, full of evil, corruption and violence. So will humanity be on Judgement Day (the end of the millennium), when again our planet is destroyed, this time by fire instead of water (2 Peter 3:6-7).
The LORD invited Noah and his household to enter the ark (v. 1), and bring with him a sample of the creatures that should be preserved from the deluge that was to come (v.2-4) – it had not yet even started to rain! This reminds us of the invitation that our Saviour makes: “Come to me all you who labour and are heavy laden, and I will give you rest” (Matthew 11:28), the Gospel of repentance for remission of sins, which should be preached to all nations (Luke 24:47).
More than one hundred years earlier Noah was instructed to take a pair of each kind of animal, bird or reptile, now Noah was instructed to take seven pairs of clean animals and birds (also clean); just a couple of the unclean as before. We have no more details as to how Noah could distinguish between the clean and the unclean but he undoubtedly knew. Probably the same distinction was given to the people of Israel centuries later: the clean animals were those fit for offerings and sacrifices, ten in all (Genesis 8:20). It is estimated that nearly 45,000 animals of all varieties would fit in the ark.
God also gave a deadline of seven days for the preparations to be finished before the flood: time to put everything still missing inside the ark, and Noah and his family to settle down in it. This reminds us that after the Rapture, there will be a period of seven years of great tribulation, when humanity will still have opportunity to repent in order to enter the millennium, or be destroyed.
Noah again faithfully obeyed the command of the LORD, at the age of six hundred years, and he entered the ark with his wife, three sons and their wives, and animals, as stated again in verses 13 to 16, and the rain came only a week afterwards. Nowhere do we read that Noah was to hunt or gather the animals to bring them into the ark; and in fact creation, with Noah, was being directed by the Creator; so as the animals paraded before Adam for him to give them their names, now, without difficulty to Noah, they headed in pairs into the ark. This reminds us that we should not worry about details that are beyond our control, when we proceed in obedience to the LORD: let us dedicate ourselves to the work given to us, and leave the rest to Him
A week later, when the LORD had closed the door after Noah, the flood came. The flood and its terrible consequences were not the responsibility of Noah, neither could he help anyone.
The flood was caused by the rupture of all the fountains of the great deep, and the opening of the floodgates of heaven. The great deep in biblical language is the sea: this makes us understand that on the third day of creation God gathered the waters into one place, forming the dry land also in a single block. There was also a much larger amount of water in the atmosphere. The flood resulted from a cataclysm in which a great part of the water fell from the atmosphere, and the water contained in the only ocean was poured upon the dry land (geologists know that the continents all belong to one original block, confirming the biblical account). At that time there were probably none of the high mountain ridges we have now.
This cataclysm lasted forty days and at the end of this time all the land was under water. The mountains of Ararat currently rise to 5,185 meters above sea level, but they could be much lower at that time, and it seems that they were the highest. It was a deluge of universal proportions: there are more than 270 different accounts of the flood, coming from all over the world.
After the forty days of deluge, the rain stopped enough so that the water level remained at its highest point for five months, seven metres above the highest mountain peak. The entire human population (probably no one was using boats or ships at the time) and all animals that lived on Earth died out, except those who were in the ark.
1 Then the LORD said to Noah, "Come into the ark, you and all your household, because I have seen that you are righteous before Me in this generation.
:2 You shall take with you seven each of every clean animal, a male and his female; two each of animals that are unclean, a male and his female;
3 also seven each of birds of the air, male and female, to keep the species alive on the face of all the earth.
4 For after seven more days I will cause it to rain on the earth forty days and forty nights, and I will destroy from the face of the earth all living things that I have made."
5 And Noah did according to all that the LORD commanded him.
6 Noah was six hundred years old when the floodwaters were on the earth.
7 So Noah, with his sons, his wife, and his sons' wives, went into the ark because of the waters of the flood.
8 Of clean animals, of animals that are unclean, of birds, and of everything that creeps on the earth,
9 two by two they went into the ark to Noah, male and female, as God had commanded Noah.
10 And it came to pass after seven days that the waters of the flood were on the earth.
11 In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, on that day all the fountains of the great deep were broken up, and the windows of heaven were opened.
12 And the rain was on the earth forty days and forty nights.
13 On the very same day Noah and Noah's sons, Shem, Ham, and Japheth, and Noah's wife and the three wives of his sons with them, entered the ark—
14 they and every beast after its kind, all cattle after their kind, every creeping thing that creeps on the earth after its kind, and every bird after its kind, every bird of every sort.
15 And they went into the ark to Noah, two by two, of all flesh in which is the breath of life.
16 So those that entered, male and female of all flesh, went in as God had commanded him; and the LORD shut him in.
17 Now the flood was on the earth forty days. The waters increased and lifted up the ark, and it rose high above the earth.
18 The waters prevailed and greatly increased on the earth, and the ark moved about on the surface of the waters.
19 And the waters prevailed exceedingly on the earth, and all the high hills under the whole heaven were covered.
20 The waters prevailed fifteen cubits upward, and the mountains were covered.
21 And all flesh died that moved on the earth: birds and cattle and beasts and every creeping thing that creeps on the earth, and every man.
22 All in whose nostrils was the breath of the spirit of life, all that was on the dry land, died.
23 So He destroyed all living things which were on the face of the ground: both man and cattle, creeping thing and bird of the air. They were destroyed from the earth. Only Noah and those who were with him in the ark remained alive.
24 And the waters prevailed on the earth one hundred and fifty days.
Genesis chapter 7