(Rom 9:14-16) What then shall we say? Is God unjust? Not at all! 15 For he says to Moses, “I will have mercy on whom I have mercy, and I will have compassion on whom I have compassion.” 16 It does not, therefore, depend on man’s desire or effort, but on God’s mercy.
Now, it’s critical at this juncture that we not jump to conclusions. Paul isn’t finished with his argument. Again, we turn to the context —
(Exo 33:17-20) And the LORD said to Moses, “I will do the very thing you have asked, because I am pleased with you and I know you by name.”
18 Then Moses said, “Now show me your glory.”
19 And the LORD said, “I will cause all my goodness to pass in front of you, and I will proclaim my name, the LORD, in your presence. I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion. 20 But,” he said, “you cannot see my face, for no one may see me and live.”
(Exo 34:6-7) And he passed in front of Moses, proclaiming, “The LORD, the LORD, the compassionate and gracious God, slow to anger, abounding in love and faithfulness, 7 maintaining love to thousands, and forgiving wickedness, rebellion and sin. Yet he does not leave the guilty unpunished; he punishes the children and their children for the sin of the fathers to the third and fourth generation.”
Paul quotes Exo 33:19, in which God declares that he will allow Moses to see his glory, although this blessing is usually denied to others. But, in context, God isn’t saying: I have the right to refuse to save anyone I please. He is saying: if I want to bless someone who pleases me above others, it’s my privilege.
Notice especially that when the story continues and God passes before Moses, God declares in very similar terms his mercy, compassion, and forgiveness, except for the “guilty.”
The NIV conceals the evident contradiction in verse 7 in the Hebrew, where “wickedness” is forgiven and “sin” cannot be forgiven. These are the same word (‘avon). The passage is a reference back to —
(Exo 20:5-6) You shall not bow down to them or worship them; for I, the LORD your God, am a jealous God, punishing the children for the sin of the fathers to the third and fourth generation of those who hate me, 6 but showing love to a thousand generations of those who love me and keep my commandments.
The second clause of 34:7 is parallel to Exo 20:5, which says the very same thing regarding idolatry, and it all makes sense if the first clause of 34:7 is taken to have the same meaning. Exo 20:6, which is closely parallel to the first clause and says that God shows love to those who love him and keep his commands.
God will show compassion on whomever he pleases, but he pleases to show compassion to “those who love me and keep my commandments.”
Now, let’s go back to,
(Rom 9:16) It does not, therefore, depend on man’s desire or effort, but on God’s mercy.
If a man, even a good man, wishes to see God’s glory, the answer is certainly “no,” because God chooses to grant that request only to a very few … except, of course, for all Christians, who will see God’s glory at the end of time. But, then, God has chosen to give his mercy to Christians.
Just so, in the parallel passages in Exodus, God chose to show his mercy to those who love him. But God is under no compulsion to do so. After all, as Exo 34:6-7 points out, both those shown mercy and those not shown mercy are guilty of iniquity. The difference is that one group loves God and another rebels against him. And God chooses to show compassion on that basis.
The point is that God can make any rule he pleases — even a rule that Paul doesn’t like — but not that God therefore makes arbitrary rules. Rather, God is merciful to those he pleases, and he pleases to show mercy to those having faith in Jesus. And Paul explained back in Rom 8 that this is because those with faith are given the Spirit and are led by the Spirit to put to death the misdeeds of the body. They are not in rebellion.