When we read the Bible with the wrong glasses on we will often miss some otherwise obvious themes and lessons. I think this is especially true with texts like Romans 9, which have become collapsed (usually by Calvinists) into a bare show of God's (seemingly arbitrary) display of His Power. But I want to propose that Paul had something more fascinating in mind than what any Christian already knows, i.e., that God is Providentially in control of all human events.
I'm coming to believe that Romans 9 isn't so much focused on salvation/heaven as it is about first-born (priestly) status being lost to the younger born. Not only is there no clear talk about heaven, hell, etc, in this chapter, but there is a pretty clear First-Born theme when you know what to look for. Consider Paul's object lessons:
- Paul's first example is Isaac being chosen over first-born Ishmael. When you read the actual story carefully, Ishmael was expelled as an illegitimate child, who mocked Isaac for being second-born (Gen 21:9-10; cf Paul says Ishmael "persecuted" Isaac, Gal 4:29-31). It is hard for us to grasp the significance of first-born status to the ancient mind, but it meant the world to them, especially when it comes to priesthood status.
- Paul's second example is of first-born Esau and second-born Jacob. God says "the elder will serve the younger," which isn't a reference to being sent to heaven/hell, but rather to supplanting birth order. Esau sold his birthright for a bowl of soup, and later on his father’s “blessing,” which likely was also a form of ordination (Gen 27:26-30).
- Paul's third example is when God tells Moses, "I will have mercy on whom I have mercy." This is not as obvious, but if you consider the context, the situation is quite striking. The context is of the Golden Calf incident, wherein the nation of Israel lost its collective priesthood status and was relegated to the Levites alone to offer sacrifices (Ex 32:25-29). The first-born son high-priest Aaron was said to be the Golden Calf ringleader (Ex 32:35), which meant it was up to second-born Moses to take upon the intercessory role of Atonement (Ex 32:30; Deut 9:18-20; Ps 106:19-23). It is within this context that God says because Moses' priestly intercession found favor in His sight, He would honor Moses' request to spare the Israelites. God was not ‘randomly’ showing mercy here as a demonstration of how He can show mercy on a whim whenever He feels like it.
- Paul's fourth example is that of Pharaoh, which was the head of the strongest nation in the world, Egypt. In some sense, Egypt/Pharaoh was first-born among the world, likely because their pagan gods were considered the strongest. The stated goal of Moses was told in Exodus 4:22-23, "You shall say to Pharaoh, ‘Thus says the Lord, Israel is my firstborn son. Let my son go that he may serve me. If you refuse to let him go, behold, I will kill your firstborn son." We know Egypt had smothered God's first-born son, and God wasn't going to let this continue. The express instructions each time Moses confronts Pharaoh is to let the Israelites go "so that they may offer sacrifices" to God (Ex 5:1, etc). It was liturgical warfare, true religion versus false, pagan God against true God. By striking down Pharaoh's first-born son, this was effectively striking down Egypt's priesthood, and thus humiliating their gods, and vindicating Yahweh as the True God.
- Paul's final example is that of the Jews versus the Gentiles. Obviously, the Jews were to be the "chosen race, royal priesthood," first-born among the nations. Yet in rejecting Jesus, they lost their status, which triggered the influx of the Gentiles into the Body, who would then become God's priests for the world, under the heading of Jesus (the Father's first-born). Hence Paul's quote from Hosea: "Those who were not my people [the Gentiles], I will call ‘my people’" (Rom 9:25).
I think there's an undeniable 'first-born son supplanted by sin' theme here that Paul is making, and it ties all the chapter together, unlike lifting a few verses here and there without any coherent thread, and missing the richness of it all. What lesson is there for God to show mercy on Moses (who was a righteous man)? If the theme was really about God showing mercy unconditionally, we should expect the major sinners like Pharaoh to be shown mercy. In each case, there is sin involved by one of the parties. It is not a 'both are sinners so let's show mercy to one of them' theme. Paul is telling the Jews of his time that all these other first-born sons lost their status, and rejecting Jesus can lead to the same for you Jews. The first-born status also being tied to priesthood also means the undercurrent is that of True Worship, which makes the real issue about glorifying God liturgically, and only secondarily about saving men. (Side note: this is why for Catholics, when Scripture is read at Mass, it is first of all a prayer to God, and only secondarily a lesson to us. This is why the Protestant “worship” being nothing more than a Glorified Bible Study is the ultimate attack on Christianity, because it removes worship of God from the main equation and shifts focus subtly onto man’s quest for knowledge.)