Corpus of Latin Ecclesiastical Writers, Vol. LV: The Letters of Augustine, Part II

390 years, which are calculated as follows: Sem, in the second year after the flood, when he was one hundred years old, begat Arfaxat, and after his birth he lived five hundred years, that is, six hundred in total. Arfaxat, born thirty-five years, begat Sale, who himself, at thirty, produced Heber, whom we read to have begotten Faleg at thirty-four years of age. Again, Faleg, having completed thirty years, begat Reu, who himself, after the thirty-second year of his birth, brought forth Serug, from whom, when he had reached thirty years, was born Nachor, who at twenty-nine years begat Thare, whom we read to have begotten Abram, Nachor, and Aran at the age of seventy. Calculate the number of years through each age, and you will find three hundred and ninety years from the birth of Sem to the generation of Abram. Moreover, Abraham died in the one hundred and seventy-fifth year of his age: by this calculation, it is found that Sem outlived his great-great-great-grandson original: "abnepoti" Abraham by thirty-five years.

6. At the same time, they also hand down that until the priesthood of Aaron, all the firstborn from the lineage of Noah, whose succession and order is described, were priests and offered sacrifices to God, and that these were the firstborn,