This is the history of the generations of Isaac, Abraham's son. Abraham became the father of Isaac.
KJV
And these are the generations of Isaac, Abraham’s son: Abraham begat Isaac:
Commentary
Commentary
And these are the generations of Isaac, Abraham's son,.... Moses, having given the genealogy of Ishmael and his posterity, returns to Isaac, the other son of Abraham, with whom and his children the following part of his history is chiefly, if not altogether concerned:
Abraham begat Isaac; for the further confirmation of his being his proper legitimate son this clause is added.
Commentary
Commentary