We are here told,

I.How long the flood was increasing - forty days, Gen 7:17. The profane world, who believed not that it would come, probably when it came flattered themselves with hopes that it would soon abate and never come to extremity; but still it increased, it prevailed. Note, 1. When God judges he will overcome. If he begin, he will make an end; his way is perfect, both in judgment and mercy. 2. The gradual approaches and advances of God's judgments, which are designed to bring sinners to repentance, are often abused to the hardening of them in their presumption.

II.To what degree they increased: they rose so high that not only the low flat countries were deluged, but to make sure work, and that none might escape, the tops of the highest mountains were overflowed - fifteen cubits, that is, seven yards and a half; so that in vain was salvation hoped for from hills or mountains, Jer 3:23. None of God's creatures are so high but his power can overtop them; and he will make them know that wherein they deal proudly he is above them. Perhaps the tops of the mountains were washed down by the strength of the waters, which helped much towards the prevailing of the waters above them; for it is said (Job 12:15), He sends out the waters, and they not only overflow, but overturn, the earth. Thus the refuge of lies was swept away, and the waters overflowed the hiding-place of those sinners (Isa 28:17), and in vain they fly to them for safety, Rev 6:16. Now the mountains departed, and the hills were removed, and nothing stood a man in stead but the covenant of peace, Isa 54:10. There is no place on earth so high as to set men out of the reach of God's judgments, Jer 49:16; Oba 1:3, Oba 1:4. God's hand will find out all his enemies, Psa 21:8. Observe how exactly they are fathomed (fifteen cubits), not by Noah's plummet, but by his knowledge who weighs the waters by measure, Job 28:25.

III.What became of Noah's ark when the waters thus increased: It was lifted up above the earth (Gen 7:17), and went upon the face of the waters, Gen 7:18. When all other buildings were demolished by the waters, and buried under them, the ark alone subsisted. Observe, 1. The waters which broke down every thing else bore up the ark. That which to unbelievers is a savour of death unto death is to the faithful a savour of life unto life. 2. The more the waters increased the higher the ark was lifted up towards heaven. Thus sanctified afflictions are spiritual promotions; and as troubles abound consolations much more abound.

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.

And all flesh died that moved upon the earth,.... That had animal life in them, of which motion was a sign:

both of fowl, and of cattle, and of beast, and of every creeping thing that creepeth on the earth; excepting those that were in the ark. This general destruction of the creatures, as it was for the sins of men, whose they were, and by whom they were abused, and is expressive of God's hatred of sin, and of his holiness and justice in the punishment of it; so, on the other hand, it is a display both of the wisdom of God, in causing a decrease of the creatures, in proportion to the decrease of men, who now would not need so many; and of the goodness of God to those that were spared, that so the beasts of the field, especially the wilder sort, might not multiply against them, and prevail over them, see Exo 23:29.

and every man: except those in the ark; and the number of them is supposed to be as great, if not greater, than of the present inhabitants of the earth, by those who are skilful in the calculation of the increase of men. It is thought it may be easily allowed, that their number amounted to eleven billion; and some have made their number to be eighty billion (p). The Apostle Peter calls them, the world of the ungodly, Pe2 2:5.

(p) Scheuchzer. Physica Sacra, vol. 1. p. 55.

the waters increased, and bare up the ark--It seems to have been raised so gradually as to be scarcely perceptible to its occupants.