Romans 9:17-18 meaning

God shows mercy to whom He chooses, shows favor to whom He chooses, and He opposes whom He chooses. In the example of Pharaoh, Pharaoh was already opposed to God, and resisted every method God used to communicate with him, whether it was Moses and Aaron literally telling Pharaoh what God commanded, or the many plagues God sent to cause chaos in Pharaoh's kingdom. 

God knew Pharaoh would defy Him at every turn, which is why God allowed him to be Pharaoh in the first place. He used a powerful, rebellious ruler to show that He, God, was vastly more powerful, and that the whole earth should see this. 

Paul references Exodus 9:16, citing a verse that tells us what God told Moses to say to Pharaoh. For the Scripture says to Pharaoh, "For this very purpose I raised you up, to demonstrate My power in you, and that My name might be proclaimed throughout the whole earth (v 17)." 

Pharaoh sums up his own rebellious attitude toward God in Exodus 5, where he asks Moses, "Who is the Lord that I should obey His voice to let Israel go? I do not know the Lord, and besides, I will not let Israel go" (Exodus 5:2). What follows Pharaoh's rejection are the ten plagues of Egypt, resulting finally in the death of Pharaoh's son. Even then, Pharaoh pursues the Israelites to reclaim them as his slaves. 

God works against this wicked king, hardening, burdening him with commandments and plagues and devastation, and Pharaoh diligently replies, "Who is the Lord that I should obey His voice?" The legacy of Pharaoh is just as Scripture claims: God showed His power, God rescued His people, and the world knew of the fall of that wicked king from whom the Israelites were set free, because of God's might and God's will. 

As a result of Pharaoh's rejection, God was able to deliver Israel, and His power was proclaimed throughout the whole earth. This might be viewed as an example of God working all things to the good for those who love Him, as we saw at the end of the previous chapter (Romans 8:28-29). 

It is encouraging that the book of Romans is so clear about God's purpose for those who believe in Him. Anyone who will receive the free gift of God's grace by faith will be adopted as a child into God's family. But this is because that is what He has promised to do, and what He chooses to do. He is not obligated. 

Further, God rewards those whom He decides to reward based on His own judgement. He favors whom He decides to favor: So then He has mercy on whom He desires, and He hardens whom He desires (v 18). 

God further hardened Pharaoh after Pharaoh first hardened his own heart (Exodus 8:15). God judged Pharaoh by giving him more of what he already chosen. This is similar to God judging unrighteousness by turning us over to our own flesh, giving us the natural consequence of our choices (Romans 1:24, 26, 28). 

As a result, Egypt was judged. When Paul prays for Onesiphorus to gain great rewards from God because of his care for Paul, he prays that the Lord might "grant mercy" to him (2 Timothy 1:16). This is because all favor and all reward that comes from God is an act of His mercy, because God is beholden to no one. However, God tells us what pleases Him, and honors His promises. Therefore, He is trustworthy. 

When it comes to being justified in His sight through the blood of Jesus, clearly God promises His grace/favor to freely give justification in His sight to all who believe (John 3:14-15). He is not obligated to do so but has promised that He will do so. Since God is God, He will do as He promised and the gifts of God are irrevocable (Romans 11:29) As this passage demonstrates, the choice we make of who to trust has dramatic consequences.

Pharaoh trusted himself and had hardened his own heart before God hardened it further. When Paul discussed God's wrath in Romans 1, he made it clear that God's wrath is poured out when people insist on following their own heart, and God eventually "gave them over" until the point where they had a debased mind (Romans 1:28). Anyone who chooses their own way experiences negative consequences while God's way leads to life.