Verses 8-12 form a single complex sentence. V. 13 is a concluding exhortation based upon the contents of vv. 8-12.
3.8 ἐμοὶ τῷ ἐλαχιστοτέρῳ πάντων ἁγίων ἐδόθη ἡ χάρις αὕτη, τοῖς ἔθνεσιν εὐαγγελίσασθαι τὸ ἀνεξιχνίαστον πλοῦτος τοῦ Χριστοῦ
ἐμοὶ τῷ ἐλαχιστοτέρῳ πάντων ἁγίων – The dative pronoun marks the indirect object of ἐδόθη, but is at the head of the clause. It is modified appositionally by the adjective ἐλαχιστοτέρῳ. This form is a little unusual in that ἐλάχιστος already is a superlative, but to it is added the ending that normally marks a comparative adjective, i.e., “more least.” Presumably this formation stresses the presumed insignificance of this person. The comparative is itself qualified by a genitive of comparison. The use of πάντων has an inclusive sense, i.e., there are no other “holy ones” beyond this group to which this person can be compared.
ἐδόθη ἡ χάρις αὕτη — ἐδόθη is aorist indicative passive, with God again the presumed agent. The subject is modified by the demonstrative pronoun αὕτη to make sure the anaphoric reference to χάρις is discerned by the audience.
τοῖς ἔθνεσιν εὐαγγελίσασθαι – The infinitive εὐαγγελίσασθαι presumably expresses the purpose for the previous gift of God’s favour. This verb takes a direct and indicate object, which is marked by the dative. Paul indicates that the nations are the recipients of this good news message.
τὸ ἀνεξιχνίαστον πλοῦτος τοῦ Χριστοῦ — The accusative object defines the content of the good news that is communicated. The noun πλοῦτος is defined by an adjective, as well as a genitive construction. The genitive may define the source of the wealth or it might define the nature of the wealth, i.e., the Messiah himself. The adjective ἀνεξιχνίαστον occurs in Romans 11:33 in conjunction with ἀνεξεραύνατος (something very difficult to grasp based upon careful examination). So the adjective probably has the sense of wealth whose provision is impossible to comprehend, unfathomable. πλοῦτος here is the neuter noun πλοῦτος, -εος.
3. 9 καὶ φωτίσαι [πάντας] τίς ἡ οἰκονομία τοῦ μυστηρίου τοῦ ἀποκεκρυμμένου ἀπὸ τῶν αἰώνων ἐν τῷ θεῷ τῷ τὰ πάντα κτίσαντι,
καὶ φωτίσαι [πάντας] – The infinitive continues the infinitive of purpose construction and is compounded with εὐαγγελίσασθαι. φωτίζω describes a kind of revelation – causing something to come into the light. This occurrence has a double object, namely πάντας and the indirect question. The brackets indicate some uncertainty on the part of the editors of NA 28 whether the word enclosed is part of the original text. It contrasts with the following ἀποκεκρυμμένου.
τίς — The interrogative marks the indirect question. It is nominative because the question is a verbless clause and it functions as the predicate nominative (ἡ οἰκονομία…τίς).
ἡ οἰκονομία τοῦ μυστηρίου — ἡ οἰκονομία functions as the subject of the verbless clause (marked by the article). It describes a plan, scheme or arrangement and Paul uses it several times to describe God’s mission and how it is unfolding. The genitive τοῦ μυστηρίου defines the content or referent of the plan, i.e., what it is about and entails. It could be an expexegetical genitive. Paul uses this term frequently to describe God’s actions in Christ – a secret plan which now he has revealed.
τοῦ ἀποκεκρυμμένου ἀπὸ τῶν αἰώνων – The perfect passive participle ἀποκεκρυμμένου is adjectival, modifying μυστηρίου. The perfect aspect suggests a stative sense, “remained/stayed hidden.” The prepositional phrase indicates the point from which this hiddenness began, i.e., “the ages.” History in antiquity is often conceived as a series of “ages” or periods.
ἐν τῷ θεῷ τῷ τὰ πάντα κτίσαντι – The preposition ἐν when accompanied by reference to a person often suggests a sense of agency, i.e., “by means/action of God.” However, it might also have a locative sense, i.e., “in the realm of God, where he rules.” The second τῷ functions to define the participle κτίσαντι as adjectival. God is defined as “the one who created the universe.” The implication is that what he has done in Christ is part of his plan for his creation.
3.10 ἵνα γνωρισθῇ νῦν ταῖς ἀρχαῖς καὶ ταῖς ἐξουσίαις ἐν τοῖς ἐπουρανίοις διὰ τῆς ἐκκλησίας ἡ πολυποίκιλος σοφία τοῦ θεοῦ,
ἵνα γνωρισθῇ νῦν – With what verb/clause should we connect this purpose/result clause? One candidate is the initial ἐδόθη ἡ χάρις in v.8. The verb is aorist passive subjunctive – another verb of knowing. It is modified by the temporal adverb νῦν which probably contrasts with the previously mentioned “ages.” See v. 5.
ταῖς ἀρχαῖς καὶ ταῖς ἐξουσίαις ἐν τοῖς ἐπουρανίοις – The verb γνωρίζω takes a direct and indirect object. Being in passive voice, only the indirect object is defined. It is unclear whether the locative prepositional phrase modifies both elements or only ταῖς ἐξουσίαις. Both nouns have articles and so one might presume the prepositional phrase modifies only the second noun. The ἀρχαί might then refer to human rulers and the “powers in the heavens” to spiritual beings such as angels and demons.
διὰ τῆς ἐκκλησίας – This adverbial prepositional phrase describes the means by which God’s wisdom is made known. What does the singular form imply about this assembly? Paul does not think it necessary to add any qualifiers to this noun.
ἡ πολυποίκιλος σοφία τοῦ θεοῦ — The nominative case marks this as the subject of the verb in the ἵνα clause. The secret plan of God becomes God’s diverse wisdom. The genitive defines whose wisdom is under discussion. It might be classified as a subjective genitive, i.e., the richly diverse wisdom displayed by God.
3.11 κατὰ πρόθεσιν τῶν αἰώνων ἣν ἐποίησεν ἐν τῷ Χριστῷ Ἰησοῦ τῷ κυρίῳ ἡμῶν,
κατὰ πρόθεσιν τῶν αἰώνων – It is difficult to discern what κατὰ πρόθεσιν modifies as an adverbial prepositional phrase. NA 28 place a comma after σόφια τοῦ θεοῦ suggesting that it does not relate to the ἵνα clause. Rather it adds further information about the main clause expressed in v. 8. However, it could modify the two infinitives of purpose or the action described in the ἵνα clause. Or perhaps it qualifies all the divine actions defined in vv. 8-10. Whatever it modifies, it defines the standard by which these things occur – in accord with a plan/purpose for the ages. The genitive indicates the scope of the plan.
ἣν ἐποίησεν – The relative clause modifies πρόθεσιν and the relative pronoun is the object of the verb. The verb is aorist active indicative with God as the subject and defines a completed action.
ἐν τῷ Χριστῷ Ἰησοῦ τῷ κυρίῳ ἡμῶν – The adverbial prepositional phrase qualifies the verb ἐποίησεν. It probably describes the means or manner in which the plan was activated and accomplished. Paul uses the full title of Jesus which expresses all dimensions of Jesus’ person and work, past, present and future. Note that Χριστός is the first element, i.e., his messianic status and role, with κύριος functioning appositionally (“by means of the Messiah, Jesus, our Lord”). ἡμῶν is genitive of subordination.
3.12 ἐν ᾧ ἔχομεν τὴν παρρησίαν καὶ προσαγωγὴν ἐν πεποιθήσει διὰ τῆς πίστεως αὐτοῦ.
ἐν ᾧ ἔχομεν – The relative clause further qualifies Χριστῷ. The preposition picks up the sense of means/manner, i.e., “by means of whom….” The verb is present active indicative and shifts attention from a completed action to something that is a continuing action.
τὴν παρρησίαν καὶ προσαγωγὴν – Both nouns are compounded together with a single article and function as the object of the verb. They define “boldness and access” presumably with reference to believers’ relationship with God.
ἐν πεποιθήσει – This prepositional phrase probably relates to the two preceding nouns and defines the manner which characterizes this boldness and access. The noun describes “reliant confidence.”
διὰ τῆς πίστεως αὐτοῦ — Another adverbial prepositional phrase which defines the means by which this boldness and access is acquired, i.e., “through faith in him” or “through his faithfulness.” The genitive pronoun could be objective or subjective.
3.13. διὸ αἰτοῦμαι μὴ ἐγκακεῖν ἐν ταῖς θλίψεσίν μου ὑπὲρ ὑμῶν, ἥτις ἐστιν δόξα ὑμῶν.
διὸ αἰτοῦμαι – The particle διό has a summarizing function. The verb is present middle indicative and describes pleading.
μὴ ἐγκακεῖν – The infinitive marks indirect speech and may indicate a prohibition, i.e., “do not….” The verb form is a present active infinitive and refers to discouragement, failure of motivation. Cf. Gal. 6:9. The addressee presumably is the letter’s recipients.
ἐν ταῖς θλίψεσίν μου – An adverbial prepositional phrase that qualifies the infinitive and defines the basis for or cause of the discouragement. The pronoun is probably an objective genitive, i.e., the afflictions happening to me.
ὑπὲρ ὑμῶν – Paul affirms that such afflictions are “for you, on your behalf.”
ἥτις ἐστιν δόξα ὑμῶν. – A relative clause introduced by ἥτις which technically has the sense “which are the sort that….” The pronoun is the subject and its antecedent is the preceding θλίψις, even though there is lack of concord with respect to number. δόξα is a predicate nominative.