When men began to multiply - It was not at this time that men began to multiply, but the inspired penman speaks now of a fact which had taken place long before. As there is a distinction made here between men and those called the sons of God, it is generally supposed that the immediate posterity of Cain and that of Seth are intended. The first were mere men, such as fallen nature may produce, degenerate sons of a degenerate father, governed by the desire of the flesh, the desire of the eye, and the pride of life. The others were sons of God, not angels, as some have dreamed, but such as were, according to our Lord's doctrine, born again, born from above, John 3:3, John 3:5,John 3:6, etc., and made children of God by the influence of the Holy Spirit, Galatians 5:6. The former were apostates from the true religion, the latter were those among whom it was preserved and cultivated. Dr. Wall supposes the first verses of this chapter should be paraphrased thus: "When men began to multiply on the earth, the chief men took wives of all the handsome poor women they chose. There were tyrants in the earth in those days; and also after the antediluvian days powerful men had unlawful connections with the inferior women, and the children which sprang from this illicit commerce were the renowned heroes of antiquity, of whom the heathens made their gods."

A.M.

1556. B.C.

2448. to multiply.

Genesis 1:28 And God blessed them, and God said to them, Be fruitful, and multiply, and replenish the earth, and subdue it...

Covenanting Performed in Former Ages with Approbation from Above.
That the Lord gave special token of his approbation of the exercise of Covenanting, it belongs to this place to show. His approval of the duty was seen when he unfolded the promises of the Everlasting Covenant to his people, while they endeavoured to perform it; and his approval thereof is continually seen in his fulfilment to them of these promises. The special manifestations of his regard, made to them while attending to the service before him, belonged to one or other, or both, of those exhibitions …
John Cunningham—The Ordinance of Covenanting

Noah's Faith, Fear, Obedience, and Salvation
We may take pleasure in thinking of Noah as a kind of contrast to Enoch. Enoch was taken away from the evil to come: he saw not the flood, nor heard the wailing of those who were swept away by the waterfloods. His was a delightful deliverance from the harvest of wrath which followed the universal godlessness of the race. It was not his to fight the battle of righteousness to the bitter end; but by a secret rapture he avoided death, and escaped those evil days in which his grandson's lot was cast. …
Charles Haddon Spurgeon—Spurgeon's Sermons Volume 36: 1890

Covenanting Enforced by the Grant of Covenant Signs and Seals.
To declare emphatically that the people of God are a covenant people, various signs were in sovereignty vouchsafed. The lights in the firmament of heaven were appointed to be for signs, affording direction to the mariner, the husbandman, and others. Miracles wrought on memorable occasions, were constituted signs or tokens of God's universal government. The gracious grant of covenant signs was made in order to proclaim the truth of the existence of God's covenant with his people, to urge the performance …
John Cunningham—The Ordinance of Covenanting