Genesis 5:32

32.And Noah was five hundred years old. Concerning the fathers whom Moses has hitherto enumerated, it is not easy to conjecture whether each of them was the first born of his family or not; for he only wished to follow the continued succession of the Church. But God, to prevent men from being elated by a vain confidence in the flesh, frequently chooses for himself those who are posterior in the order of nature. I am, therefore, uncertain whether Moses has recorded the catalogue of those whom God preferred to others; or of those who, by right of primogeniture, held the chief rank among their brethren; I am also uncertain how many sons each had. With respect to Noah, it plainly appears that he had no more than three sons; and this Moses purposely declares the more frequently, that we may know that the whole of his family was preserved. But they, in my opinion, err, who think that in this place the chastity of Noah is proclaimed, because he led a single life through nearly five centuries. For it is not said that he was unmarried till that time; nor even in what year of his life he had begun to be a father. But, in simply mentioning the time in which he was warned of the future deluge, Moses also adds, that at the same time, or thereabouts, he was the father of three sons; not that he already had them, but because they were born not long afterwards. That he had, indeed, survived his five hundredth year before Shem was born, will be evident from the eleventh chapter (Genesis 11:1); concerning the other two nothing is known with certainty, except that Japheth was the younger. (258) It is wonderful that from the time when he had received the dreadful message respecting the destruction of the human race, he was not prevented, by the greatness of his grief, from intercourse with his wife; but it was necessary that some remains should survive, because this family was destined for the restoration of the second world. Although we do not read at what time his sons took wives, I yet think it was done long before the deluge; but they were unfruitful by the providence of God, who had determined to preserve only eight souls.