Man's sin is the cause of the deluge. Noe is commanded to build the ark.

 1 And after that men began to be multiplied upon the earth, and daughters were born to them,  2 The sons of God seeing the daughters of men, that they were fair, took to themselves wives of all which they chose.  3 And God said: My spirit shall not remain in man for ever, because he is flesh, and his days shall be a hundred and twenty years.  4 Now giants were upon the earth in those days. For after the sons of God went in to the daughters of men, and they brought forth children, these are the mighty men of old, men of renown.  5 And God seeing that the wickedness of men was great on the earth, and that all the thought of their heart was bent upon evil at all times,

[2] "The sons of God": The descendants of Seth and Enos are here called sons of God from their religion and piety: whereas the ungodly race of Cain, who by their carnal affections lay grovelling upon the earth, are called the children of men. The unhappy consequence of the former marrying with the latter, ought to be a warning to Christians to be very circumspect in their marriages; and not to suffer themselves to be determined in their choice by their carnal passion, to the prejudice of virtue or religion.

[3] "His days shall be": The meaning is, that man's days, which before the flood were usually 900 years, should now be reduced to 120 years. Or rather, that God would allow men this term of 120 years, for their repentance and conversion, before he would send the deluge.

[4] "Giants": It is likely the generality of men before the flood were of a gigantic stature in comparison with what men now are. But these here spoken of are called giants, as being not only tall in stature, but violent and savage in their dispositions, and mere monsters of cruelty and lust.

 6 It repented him that he had made man on the earth. And being touched inwardly with sorrow of heart,  7 He said: I will destroy man, whom I have created, from the face of the earth, from man even to beasts, from the creeping thing even to the fowls of the air, for it repenteth me that I have made them.  8 But Noe found grace before the Lord.  9 These are the generations of Noe: Noe was a just and perfect man in his generations, he walked with God.  10 And he begot three sons, Sem, Cham, and Japheth.

[6] "It repented him": God, who is unchangeable, is not capable of repentance, grief, or any other passion. But these expressions are used to declare the enormity of the sins of men, which was so provoking as to determine their Creator to destroy these his creatures, whom before he had so much favoured.

 11 And the earth was corrupted before God, and was filled with iniquity.  12 And when God had seen that the earth was corrupted (for all flesh had corrupted its way upon the earth,)  13 He said to Noe: The end of all flesh is come before me, the earth is filled with iniquity through them, and I will destroy them with the earth.  14 Make thee an ark of timber planks: thou shalt make little rooms in the ark, and thou shalt pitch it within and without.  15 And thus shalt thou make it: The length of the ark shall be three hundred cubits: the breadth of it fifty cubits, and the height of it thirty cubits.

[15] "Three hundred cubits": The ark, according to the dimensions here set down, contained four hundred and fifty thousand square cubits; which was more than enough to contain all the kinds of living creatures, with all necessary provisions: even supposing the cubits here spoken of to have been only a foot and a half each, which was the least kind of cubits.

 16 Thou shalt make a window in the ark, and in a cubit shalt thou finish the top of it: and the door of the ark thou shalt set in the side: with lower, middle chambers, and third stories shalt thou make it.  17 Behold I will bring the waters of a great flood upon the earth, to destroy all flesh, wherein is the breath of life, under heaven. All things that are in the earth shall be consumed.  18 And I will establish my covenant with thee, and thou shalt enter into the ark, thou and thy sons, and thy wife, and the wives of thy sons with thee.  19 And of every living creature of all flesh, thou shalt bring two of a sort into the ark, that they may live with thee: of the male sex, and the female.  20 Of fowls according to their kind, and of beasts in their kind, and of every thing that creepeth on the earth according to its kind; two of every sort shall go in with thee, that they may live.

 21 Thou shalt take unto thee of all food that may be eaten, and thou shalt lay it up with thee: and it shall be food for thee and them.  22 And Noe did all things which God commanded him.