פירוש על בראשית 10:21

אבי כל בני עבר THE FATHER OF ALL THE CHILDREN OF EBER — (עבר means the “side” or “ other side” of a river) — The father of all the children of עבר הנהר, the other side of the River (Euphrates), was Shem.

AND UNTO SHEM, TO HIM ALSO WERE CHILDREN BORN. Since Scripture delayed the narration of the generations of Shem and related the generations of his younger brother as if Shem had no children, it therefore says here, to him also.

ולשם יולד, the formulation suggests that the son born to Shem resembled his father in his good qualities, the son in question being עבר.