Augustine of Hippo produced a first concise interpretation of Romans 9 to which reformed commentators approach Romans 9:14-25. Expositing Romans 9:16, Augustine noted that God “loved Jacob in unmerited mercy, yet hated Esau with merited justice”. He explained,
Since this judgment [of wrath] was due them both, the former learned from what happened to the other that the fact that he had not, with equal merit, incurred the same penalty gave him no ground to boast of his own distinctive merits (Augustine 2005: n.p)
None, according Augustine, “is set free saved by unmerited mercy” and none “is damned save by a merited condemnation.”(ibid). God chose some individuals to bestow His mercy and others, the not chosen, His justice. Augustine expounded,
Certainly wrath is not repaid unless it is due, lest there be unrighteousness with God; but mercy, even when it is bestowed, and not due, is not unrighteousness with God. And hence, let the vessels of mercy understand how freely mercy is afforded to them, because to the vessels of wrath with whom they have common cause and measure of perdition, is repaid wrath, righteous and due.(Augustine 1887: 423–4)
Martin Luther understood Romans 9:15 to mean, “I will have mercy on whom I intended to have mercy, or whom I predestinated for mercy.”(Luther 1976: 139), He went further,
“I will have compassion on whom I will have compassion (9:15). That means: I will give grace, in time and life, to him concerning whom I purposed from eternity to show mercy. On him will I have compassion and forgive his sin in time and life whom I forgave and pardoned from all eternity.(ibid)
Reformed Approach to Romans 9:14-25