John Calvin Commentary Genesis 5:32

"And Noah was five hundred years old: And Noah begat Shem, Ham, and Japheth." — Genesis 5:32 (ASV)

And Noah was five hundred years old. Concerning the fathers whom Moses has previously listed, it is not easy to surmise whether each of them was the firstborn of his family, as Moses only wished to follow the continuous succession of the Church. But God, to prevent people from being elated by a vain confidence in the flesh, frequently chooses for Himself those who are later in the natural order.

Therefore, I am uncertain whether Moses recorded the list of those whom God preferred to others, or of those who, by right of primogeniture, held the chief rank among their brothers. I am also uncertain how many sons each one had. With respect to Noah, it clearly appears that he had no more than three sons, and Moses purposely declares this more frequently so that we may know that his entire family was preserved.

However, in my opinion, those who think that Noah's chastity is proclaimed here—because he supposedly remained single for nearly five centuries—are mistaken. For it is not said that he was unmarried until that time, nor even in what year of his life he began to be a father.

Rather, in simply mentioning the time when he was warned of the future deluge, Moses also adds that, around the same time, he became the father of three sons—not that he already had them, but because they were born not long afterward. That he had indeed survived his five hundredth year before Shem was born is evident from Genesis 11:1. Concerning the other two, nothing is known with certainty, except that Japheth was the younger.

It is remarkable that, from the time he received the dreadful message concerning the destruction of the human race, he was not prevented by the intensity of his grief from intercourse with his wife. However, it was necessary that some remnant should survive, because this family was destined for the restoration of the second world. Although we do not read when his sons took wives, I still think this occurred long before the deluge; but they remained childless by God's providence, as He had determined to preserve only eight souls.