God's Free Election.
Romans 9:6-9. We must distinguish: to be of Israel, is not to be Israel. Mere physical heredity counts for nothing: Isaac was the proper seed of Abraham, designated as the child of promise (Genesis 21:12, etc.). Here Isaac's case illustrates the sovereignty of God; in Romans 4:18-21, the efficacy of faith.
Romans 9:10-13. The case of Esau and Jacob is equally significant. Twin offspring of the same parents, the unborn babes had done nothing to achieve merit or display worth, when God said, The elder shall serve the younger, an election governing the history of the descendant peoples (Malachi 1:2 f.*).
Romans 9:14. No Jew would deem God unjust in such preferences; the question of Romans 9:14 answers itself. The application to contemporary Judaism is patent.
Romans 9:15 f. The election of Jacob recalls words used to Moses: I will show mercy to whomsoever I will show mercy, etc. not that God is arbitrary in His compassions, but He is untrammeled; even Moses may not prescribe to Him. Hence the inference: it is not of him that wills, nor of him that runs (as Moses was doing then, Paul now, for Israel's salvation), but of God, etc. (cf. 1 Corinthians 3:6 f.). Dictation, like prerogative, is out of court.
Romans 9:17 f. This holds in respect of hardening too. Witness the Pharaoh of the Exodus: God raised this evil-hearted man to greatness, on purpose to demonstrate His power as the Judge of the earth. As the story shows, the monarch's defiant temper was the nemesis of unbelief; cf. Romans 1:24; Romans 1:28. In every decision God judges for Himself, despite human pleas of privilege and pride of power: Whom He will He compassionates, whom He will He hardens.