Genesis 4:20

That Cain remained alive until the seventh generation is clear. First, … it had been so decreed concerning him. Second, the length of the lives of those first generations also testifies to it. For if his father Adam remained alive until the ninth generation, that of Lamech, and was gathered from the world in the fifty-sixth year of Lamech, it is no great thing that Cain should remain until the seventh generation.

The text runs: “Methushael begot Lamech, who took two wives: the name of the one was Ada, and the name of the other Sella. And Ada brought forth Jobel; who was the father of such as dwell in tents, and of herdsmen. His brother’s name was Jubal. He was the father of all those who play the psaltery and cittara. Sella bore Tobel; he was the forger of all instruments of bronze and iron. The sister of Tobel was Noema.” This is as far as the line of descent from Cain is carried. There are eight generations in all, including Adam. The seventh is that of Lamech, who was the husband of two wives; the eighth is that of his children, among whom is the woman who is mentioned by name. What is here delicately intimated is that to the very end of its existence the earthly city will be propagated by physical births proceeding from the union of the sexes. This is why we are given the proper names of the wives of the last man mentioned as begetting children—a practice unheard of before the flood, except in the case of Eve.

He begot, he says, Ada Jabal, who was the father of those who dwell in tents and shepherds, and the name of his brother was Jubal. He was the father of those who play the harp and organ. Sella also begot Tubal-Cain, who was a forger in every kind of bronze and iron work. All these things which are said to have been found or made by the sons of Lamech relate to the cultivation, adornment, or enticements of this life: but none such are read of Abel, nor of Seth who was born in his place, nor of his grandchildren, but they are proved to have led a simple life on earth like strangers. For even if Abel was a shepherd of sheep, he did not so devote himself to this service as to build himself tents in which he could engage more comfortably in it. As for the harp and organ, it is far from likely that so great a man would have given any time to them. Indeed, anyone who diligently observes all the works made of bronze and iron will clearly recognize that if the human race had kept the natural law rightly, even after being expelled from the joys of paradise by the fault of transgression, it would by no means need all these things: whence it is evident that all these were invented by the sons of the curse, although later, as the human race degenerated from the purity of its first way of life, even good servants of God sometimes engaged in such things for the sake of social living. But with a great distinction, of course, because the wicked delighted in such things as their highest good: whereas the chosen either utterly renounce them or use them for some convenience of this life, until they reach the eternal, as a traveler uses a lodging or provisions while passing through. In short, the patriarchs lived in tents, but like strangers on earth, to distinguish them from those who lived in cities and houses as citizens of the earth. The psalmists used the harp and organ, but to praise the Lord with them: and on the contrary, the prophet reproves those who resounded with the harp, tambourine, and lyre in banquets. There were learned men among the people of God in all works of bronze and iron, as well as silver and gold: but God himself commanded them to transfer this art to the distinction of his tabernacle. The prophet also, proclaiming the joys of the Lord's incarnation, predicted that harmful works of iron would be removed and changed for the better, saying, and they shall beat their swords into plowshares, and their spears into pruning hooks; nation shall not lift up sword against nation, neither shall they learn war anymore (Isa. II, 4). Nor should it be passed over negligently that when men began to be defiled by adultery, to devote more than right to the tending of flocks, to be dissolved by musical modes, to engage in forging arts, then they were destroyed by the overhanging flood. But we must guard more diligently lest the last day find us ensnared by such things beyond measure, for the Lord, speaking of the day of judgment, mentioned this time to incite us to the study of caution, saying: For as in the days before the flood they were eating and drinking, marrying and giving in marriage, until the day when Noah entered the ark, and they did not know until the flood came and took them all away; so will be the coming of the Son of Man (Matt. XXIV, 38).