Commentary on the Bible, by Adam Clarke, , at sacred-texts.com
God informs Noah that within seven days he shall send a rain upon the earth, that shall continue for forty days and nights; and therefore commands him to take his family, with the different clean and unclean animals, and enter the ark, Gen 7:1-4. This command punctually obeyed, Gen 7:5-9. In the seventeenth day of the second month, in the six hundredth year of Noah's life, the waters, from the opened windows of heaven, and the broken up fountains of the great deep, were poured out upon the earth, Gen 7:10-12. The different quadrupeds, fowls, and reptiles come unto Noah, and the Lord shuts him and them in, Gen 7:13-16. The waters increase, and the ark floats, Gen 7:17. The whole earth is covered with water fifteen cubits above the highest mountains, Gen 7:18-20. All terrestrial animals die, Gen 7:21-23. And the waters prevail one hundred and fifty days, Gen 7:24.
Thee have I seen righteous - See the note on Gen 6:8
Of every clean beast - So we find the distinction between clean and unclean animals existed long before the Mosaic law. This distinction seems to have been originally designed to mark those animals which were proper for sacrifice and food, from those that were not. See Leviticus 11.
For yet seven days - God spoke these words probably on the seventh or Sabbath day, and the days of the ensuing week were employed in entering the ark, in embarking the mighty troop, for whose reception ample provision had been already made.
Forty days - This period became afterwards sacred, and was considered a proper space for humiliation. Moses fasted forty days, Deu 9:9, Deu 9:11; so did Elijah, Kg1 19:8; so did our Lord, Mat 4:2. Forty days' respite were given to the Ninevites that they might repent, Jon 3:4; and thrice forty (one hundred and twenty) years were given to the old world for the same gracious purpose, Gen 6:3. The forty days of Lent, in commemoration of our Lord's fasting, have a reference to the same thing; as each of these seems to be deduced from this primitive judgment.
In the six hundredth year, etc. - This must have been in the beginning of the six hundredth year of his life; for he was a year in the ark, Gen 8:13; and lived three hundred and fifty years after the flood, and died nine hundred and fifty years old, Gen 9:29; so it is evident that, when the flood commenced, he had just entered on his six hundredth year.
Second month - The first month was Tisri, which answers to the latter half of September, and first half of October; and the second was Marcheshvan, which answers to part of October and part of November. After the deliverance from Egypt, the beginning of the year was changed from Marcheshvan to Nisan, which answers to a part of our March and April. But it is not likely that this reckoning obtained before the flood. Dr. Lightfoot very probably conjectures that Methuselah was alive in the first month of this year. And it appears, says he, how clearly the Spirit of prophecy foretold of things to come, when it directed his father Enoch almost a thousand years before to name him Methuselah, which signifies they die by a dart; or, he dieth, and then is the dart; or, he dieth, end then it is sent. And thus Adam and Methuselah had measured the whole time between the creation and the flood, and lived above two hundred and forty years together. See Genesis 5 at the end, Gen 5:32 (note).
Were all the fountains of the great deep broken up, and the windows of heaven were opened - It appears that an immense quantity of waters occupied the center of the antediluvian earth; and as these burst forth, by the order of God, the circumambient strata must sink, in order to fill up the vacuum occasioned by the elevated waters. This is probably what is meant by breaking up the fountains of the great deep. These waters, with the seas on the earth's surface, might be deemed sufficient to drown the whole globe, as the waters now on its surface are nearly three-fourths of the whole, as has been accurately ascertained by Dr. Long. See the note on Gen 1:10.
By the opening of the windows of heaven is probably meant the precipitating all the aqueous vapours which were suspended in the whole atmosphere, so that, as Moses expresses it, Gen 1:7, the waters that were above the firmament were again united to the waters which were below the firmament, from which on the second day of creation they had been separated. A multitude of facts have proved that water itself is composed of two airs, oxygen and hydrogen; and that 85 parts of the first and 15 of the last, making 100 in the whole, will produce exactly 100 parts of water. And thus it is found that these two airs form the constituent parts of water in the above proportions. The electric spark, which is the same as lightning, passing through these airs, decomposes them and converts them to water. And to this cause we may probably attribute the rain which immediately follows the flash of lightning and peal of thunder. God therefore, by the means of lightning, might have converted the whole atmosphere into water, for the purpose of drowning the globe, had there not been a sufficiency of merely aqueous vapours suspended in the atmosphere on the second day of creation. And if the electric fluid were used on this occasion for the production of water, the incessant glare of lightning, and the continual peals of thunder, must have added indescribable horrors to the scene. See the note on Gen 8:1. These two causes concurring were amply sufficient, not only to overflow the earth, but probably to dissolve the whole terrene fabric, as some judicious naturalists have supposed: indeed, this seems determined by the word מבול mabbul, translated flood, which is derived from בל bal בלל or balal, to mix, mingle, confound, confuse, because the aqueous and terrene parts of the globe were then mixed and confounded together; and when the supernatural cause that produced this mighty change suspended its operations, the different particles of matter would settle according to their specific gravities, and thus form the various strata or beds of which the earth appears to be internally constructed. Some naturalists have controverted this sentiment, because in some cases the internal structure of the earth does not appear to justify the opinion that the various portions of matter had settled according to their specific gravities; but these anomalies may easily be accounted for, from the great changes that have taken place in different parts of the earth since the flood, by volcanic eruptions, earthquakes, etc. Some very eminent philosophers are of the opinion "that, by the breaking up of the fountains of the great deep, we are to understand an eruption of waters from the Southern Ocean." Mr. Kirwan supposes "that this is pretty evident from such animals as the elephant and rhinoceros being found in great masses in Siberia, mixed with different marine substances; whereas no animals or other substances belonging to the northern regions have been ever found in southern climates. Had these animals died natural deaths in their proper climate, their bodies would not have been found in such masses. But that they were carried no farther northward than Siberia, is evident from there being no remains of any animals besides those of whales found in the mountains of Greenland. That this great rush of waters was from the south or south-east is farther evident, he thinks, from the south and south-east sides of almost all great mountains being much steeper than their north or north-west sides, as they necessarily would be if the force of a great body of water fell upon them in that direction." On a subject like this men may innocently differ. Many think the first opinion accords best with the Hebrew text and with the phenomena of nature, for mountains do not always present the above appearance.
The rain was upon the earth - Dr. Lightfoot supposes that the rain began on the 18th day of the second month, or Marcheshvan, and that it ceased on the 28th of the third month, Cisleu.
And they went in, etc. - It was physically impossible for Noah to have collected such a vast number of tame and ferocious animals, nor could they have been retained in their wards by mere natural means. How then were they brought from various distances to the ark and preserved there? Only by the power of God. He who first miraculously brought them to Adam that he might give them their names, now brings them to Noah that he may preserve their lives. And now we may reasonably suppose that their natural enmity was so far removed or suspended that the lion might dwell with the lamb, and the wolf lie down with the kid, though each might still require his peculiar aliment. This can be no difficulty to the power of God, without the immediate interposition of which neither the deluge nor the concomitant circumstances could have taken place.
The Lord shut him in - This seems to imply that God took him under his especial protection, and as he shut Him in, so he shut the Others out. God had waited one hundred and twenty years upon that generation; they did not repent; they filled up the measure of their iniquities, and then wrath came upon them to the uttermost.
Fifteen cubits upward - Should any person object to the universality of the deluge because he may imagine there is not water sufficient to drown the whole globe in the manner here related, he may find a most satisfactory answer to all the objections he can raise on this ground in Mr. Ray's Physico-theological Discourses, 2d edit., 8vo., 1693.
Of all that was in the dry land - From this we may conclude that such animals only as could not live in the water were preserved in the ark.
And the waters prevailed upon the earth a hundred and fifty days - The breaking up of the fountains of the great deep, and the raining forty days and nights, had raised the waters fifteen cubits above the highest mountains; after which forty days it appears to have continued at this height for one hundred and fifty days more. "So," says Dr. Lightfoot, "these two sums are to be reckoned distinct, and not the forty days included in the one hundred and fifty; so that when the one hundred and fifty days were ended, there were six months and ten days of the flood past." For an improvement of this awful judgment, see the conclusion of the following chapter, Gen 8:22 (note).