Genesis 10:21 - Matthew Poole's English Annotations on the Holy Bible

Of all the children of Eber, i.e. of the Hebrews, the only church and people of God when Moses wrote, who are called Eber, Numbers 24:24, as here, the children of Eber. And he is here called the father of them peculiarly, though he had other children, because he was their father not only by natural generation, but also in respect of the promise of God, which was conveyed to them through Shem's hands, and of that faith and holiness wherein he was their predecessor and eminent pattern; even as Ham, though he had other sons, is specially called the father of Canaan, Genesis 9:22, because his father's curse rested upon him, Genesis 10:25. Object. Eber had many other children here recorded, and therefore in that sense Shem was not the father of all the children of Eber. Answ. Though Eber had other children, yet none are called in Scripture the children of Eber, or, which is all one, the Hebrews, but Abraham's posterity; even as though Abraham had divers other children, yet the Israelites are in many places peculiarly called the children of Abraham. And the ungodly Jews, when they degenerate from God and godliness, God takes away their name, and denieth them to be Jews, Romans 2:28, and calls them Sodomites, Isaiah 1:10. And therefore no wonder if Joktan and his posterity, having, as it is probable, forsaken their father's God, and turned idolaters, be here disowned as bastards, and blotted out of the honourable catalogue of the children of Eber: see Romans 9:8. Japheth alone is here mentioned as his brother, and not Ham, because he was deservedly shut out from Shem's blessing pronounced by Noah, and was accursed of God, whereas Japheth was partaker with Shem, both in the piety exercised towards their father, and the blessing thereupon pronounced; the word brother being often applied to persons alike in condition, disposition, or manners: see Genesis 49:5. The elder. Though the words in Hebrew may seem ambiguous, yet other texts make it probable that Japheth was the elder. For Noah began to beget children in his five hundredth year, Genesis 5:32. And Shem was but a hundred years old two years after the flood, Genesis 11:10. Therefore he was not the eldest. And Ham is concluded not to be the eldest, from Genesis 9:24; of which See Poole on "Genesis 9:24"; if so, Japheth must be the eldest. And Shem is generally named first, not because he was the first-born, but because he had the privileges of the first-born, and was chief in dignity and authority in the church of God.