In the case of Rebekah who was chosen by God for Isaac we see God had foreseen two nations for he forewarned her, ‘Two nations are in thy womb and two manner of people shall be separated from thy bowels (vs.23).’ Calling and gifts of God are irrevocable. His promise to Abraham surely stood because God cannot deny himself. But free will of man must find a common basis with God. Thus Isaac had to make certain what he would do. From this example of Isaac we are able to examine more varied shades the predestination as a theological concept presents to us.
Predestination is a characteristic of Power and Wisdom of God and it is not completely hidden from man. God had acquainted Abraham in broad strokes at the outset how that would be in his case but where Isaac was concerned he had to know Him as his father did. For this reason after Abraham was buried by his sons, God appeared unto Isaac and told him ‘Go not down into Egypt..(Ge.26:2)’Interestingly enough God had let Abraham move to Egypt earlier in a similar circumstance ‘when there was a famine in the land’ (Ge.12:10). Consequently Isaac dwelt in Gerar in obedience to His commandment. Free will for a saint is to make sure the faith component is same. As mentioned earlier Predestination of God is set inherent in human interactions where free will of Isaac had to match the faith God had required of him. God blessed Isaac saying ‘I will perform the oath which I sware unto thy father (26:3).’
Coming back to Rebekah God had warned her ‘the elder shall serve the younger.’ Spiritual discernment is the backdrop of the earth where the creation account attests the earth achieved a form(Ge.1:2). As a result invisible things of God are understood by things that are made(Ro.1:20). It does not in any way stagger belief when Abel offered a better sacrifice than his brother Cain. For the same reason Jacob struggled even in the womb as he would wrestle with the angel at Peniel later on. (Ge.32:24). Spiritual discernment differentiated Cain from Abel and in the present case Esau from Jacob. Esau despised his birthright since he did not care for the spiritual significance of it. Single-mindedly Jacob pursued it and his faith prevailed over God, meaning his faith matched the same that made Abraham the friend of God.