How should we translate 9:22? There are two options.
a) "what if God, although willing to demonstrate His wrath"
b) "what if God, because willing to demonstrate His wrath"
The latter is probably correct, indicating that God patiently endures the vessels of wrath because he wants to accomplish three things: (1) he wants to demonstrate his wrath; (2) he wants to make his power known; and (3) he wants to make known the riches of his glory on vessels of mercy.
The translation because is also supported by comparing v. 22 with v. 17. Piper explains:
"Though Paul is now speaking more generally about 'vessels of wrath', the words of God to Pharaoh in Ex. 9:16 are still serving as the pattern for the way God acts. God's raising up Pharaoh and enduring him through a ten-fold recalcitrance was not in spite of his desire to show his power but because of his desire to show it. God could have destroyed Pharaoh after any one of his acts of disobedience, and the reason he did not was that he might 'multiply his wonders in the land of Egypt' (Ex. 11:9). By 'sustaining and tolerating' Pharaoh again and again God accomplished his purpose to show his power in the plagues and finally to win renown in Pharaoh's overthrow at the Red Sea (cf. the purpose mentioned in Ex. 7:3-5; 9:14-16; 10:1; 11:9; 14:4,17-18). Therefore, since Rom. 9:22 uses the same language as 9:17, it is more probable that God's desire to show his wrath and make known his power is the cause of his sustaining and tolerating vessels of wrath than that this sustaining and tolerating are in spite of that desire" (188-89).
The third of these three purposes is clearly ultimate, the other two being subordinate. In other words, the primary purpose for which God manifests his wrath on vessels of destruction is so that his mercy might be seen as all the more glorious. "The remarkable thing is that the revelation of this treasure of glory which the church will experience as mercy, is accomplished, at least in part, by God's patiently sustaining and tolerating vessels of wrath set for destruction" (Piper, 168-69).
Second, what does it mean to say God patiently endured vessels of wrath? Apparently, God is patiently holding back immediate judgment so that the reprobate might continue to store up wrath for themselves and in this way make possible an even greater display of God's power and judgment. "The implication is that it would have been just and righteous for him to destroy them immediately" (Schreiner, 520). In dealing with Pharaoh, God endured his repeated refusal to let the people go in order that he might turn each occasion into an opportunity to display his power (Ex. 14:1-4,14). Also, with a greater measure of sin comes a greater display of wrath, which in turn sheds an even greater light on the glory of mercy towards those who themselves deserved judgment no less than the others.
Third, the vessels of mercy in v. 23 are explicitly said to have been prepared beforehand by God for glory. In v. 22 the vessels of wrath are said to be prepared for destruction, but by whom or by what? There are four views:
(1) the voice of the Greek participle may be middle, not passive; hence the vessels of wrath are conceived as having prepared themselves for destruction (ostensibly through their rebellion and unrepentant unbelief);
The direct middle, in which the subject acts directly on himself ('Judas hung himself'), should be distinguished from the indirect middle, in which the subject acts on his own behalf ('for himself').
(2) prepared for destruction is simply a descriptive phrase without implying any agent of the preparation;
(3) Paul deliberately expresses it this way to leave the issue shrouded in a mystery;
(4) God is the agent or cause by whom the vessels of wrath are prepared for destruction.
[The following is included for those with a knowledge of Greek who might wish to know why the use of the direct middle (i.e., option 1 above) is highly unlikely here: "First, grammatically, the direct middle is quite rare and is used almost exclusively in certain idiomatic expressions, especially where the verb is used consistently with such a notion (as in the verbs for putting on clothes). This is decidedly not the case with katartizo: nowhere else in the NT does it occur as a direct middle. Second, in the perfect tense, the middle-passive form is always to be taken as a passive in the NT (Luke 6:40; 1 Cor. 1:10; Heb. 11:3) ? a fact that, in the least, argues against an idiomatic use of this verb as a direct middle. Third, the lexical nuance of katartizo, coupled with the perfect tense, suggests something of a 'done deal.' Although some commentators suggest that the verb means that the vessels are ready for destruction, both the lexical nuance of complete preparation and the grammatical nuance of the perfect tense are against this. Fourth, the context argues strongly for a passive and completed notion. In v. 20 the vessel is shaped by God's will, not its own ('Will that which is molded say its maker, "why have you made me this way?"'). In v. 21, Pauls asks a question with ouk (thus expecting a positive answer): Is not the destiny of the vessels (one for honor, one for dishonor) entirely predetermined by their Creator? Verse 22 is the answer to that question. To argue, then, that katertismena is a direct middle seems to fly in the face of grammar (the normal use of the voice and tense), lexeme, and context" (Daniel B. Wallace, Greek Grammar Beyond the Basics: An Exegetical Syntax of the New Testament [Zondervan, 1996), 418).]