21 Or “He did this by revealing”; Grk “making known, revealing.” Verse 9 begins with a participle dependent on “lavished” in v. 8; the adverbial participle could be understood as temporal (“when he revealed”), which would be contemporaneous to the action of the finite verb “lavished,” or as means (“by revealing”). The participle has been translated here with the temporal nuance to allow for means to also be a possible interpretation. If the translation focused instead upon means, the temporal nuance would be lost as the time frame for the action of the participle would become indistinct.
22 Or “mystery.” In the NT μυστήριον (mustērion) refers to a divine secret previously undisclosed.
23 Or “purposed,” “publicly displayed.” Cf. Rom 3:25.
24 Grk “in him”; the referent (Christ) has been specified in the translation for the sake of clarity. In Christ. has “in himself” as though the antecedent were God the Father. Although possible, the notion of the verb set forth (Greek προτίθημι, protithēmi) implies a plan that is carried out in history (cf. Rom 1:13; 3:25) and thus more likely refers to Christ.

In other versions

making known to us the mystery of his will, according to his purpose, which he set forth in Christ

he made known to us the mystery of his will according to his good pleasure, which he purposed in Christ,

He made known to us the mystery of his will, according to his good pleasure that he purposed in Christ

God has now revealed to us his mysterious will regarding Christ—which is to fulfill his own good plan.

making known to us the mystery of his will, according to his good pleasure that he purposed in him,

Having made known unto us the mystery of his will, according to his good pleasure which he hath purposed in himself:

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