We are here told,
I. How long the flood was increasing--forty days, v. 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. iii. 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 xii. 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. xxviii. 17), and in vain they fly to them for safety, Rev. vi. 16. Now the mountains departed, and the hills were removed, and nothing stood a man in stead but the covenant of peace, Isa. liv. 10. There is no place on earth so high as to set men out of the reach of God's judgments, Jer. xlix. 16; Obad. 3, 4. God's hand will find out all his enemies, Ps. xxi. 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 xxviii. 25.
III. What became of Noah's ark when the waters thus increased: It was lifted up above the earth (v. 17), and went upon the face of the waters, v. 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.