John Gill Commentary Genesis 5:6

"And Seth lived a hundred and five years, and begat Enosh:" — Genesis 5:6 (ASV)

And Seth lived a hundred and five years, and begat Enos . Not that this was his firstborn, no doubt he had other children before this time;

but this is only mentioned, because it carried the lineage and descent directly from Adam to Noah, the father of the new world, and from whom the Messiah was to spring; whose genealogy to give is a principal view of this book, or account of generations from Adam to Noah.