W. H. Westcott · Section 4. Chapter 1.

Secondly, even Isaac's children did not all share in blessing alike. For even before they were actually born did God select the younger son Jacob to receive the place of earthly supremacy. This proves that they were not blessed on the ground of their own works, for at the time God spoke of their relative positions, they were not born; they had done neither good nor evil. Subsequently they both did evil: but God secured, by His own faithfulness to His promise, the place of supremacy for Jacob. Later, in Malachi, and when their histories had brought out their respective lives, God said, I have loved Jacob, and I have hated Esau.