As another addendum to the answers of Stephen Disraeli and Dottard:
The ESV (like most English versions) breaks up Ephesians 1:3-14 into multiple sentences, but it appears to be one long sentence in Greek.1 In particular, verses 6-7 read as follows:
... 6 εἰς ἔπαινον δόξης τῆς χάριτος αὐτοῦ ἧς ἐχαρίτωσεν ἡμᾶς ἐν τῷ ἠγαπημένῳ, 7 ἐν ᾧ ἔχομεν τὴν ἀπολύτρωσιν διὰ τοῦ αἵματος αὐτοῦ, τὴν ἄφεσιν τῶν παραπτωμάτων, κατὰ τὸ πλοῦτος τῆς χάριτος αὐτοῦ...
(SBLGNT)
which could be rendered (using the ESV translation as a base but tweaking the grammar to more literally match the Greek):
... to the praise of his glorious grace, with which he has blessed us in the Beloved, in whom we have redemption through his blood, the forgiveness of trespasses, according to the riches of his grace...
It would be natural to assume that ἐν ᾧ, "in whom," refers back to the immediately preceding τῷ ἠγαπημένῳ, "the Beloved." We can't necessarily rely on that assumption, since it is possible for a relative pronoun to refer to an antecedent farther back in the sentence.2 However, throughout this passage, there is a recurring pattern of ἐν + dative referring to Christ:3
- Verse 3: ὁ εὐλογήσας ἡμᾶς ... ἐν Χριστῷ "who has blessed us ... in Christ"
- Verse 4: ἐξελέξατο ἡμᾶς ἐν αὐτῷ "he chose us in him"
- Verse 6: ἐχαρίτωσεν ἡμᾶς ἐν τῷ ἠγαπημένῳ "he has blessed us in the Beloved"
- Verse 7: ἐν ᾧ ἔχομεν τὴν ἀπολύτρωσιν "in whom we have redemption"
- Verse 9: κατὰ τὴν εὐδοκίαν αὐτοῦ ἣν προέθετο ἐν αὐτῷ "according to his purpose which he set forth in him"
- Verse 10: ἀνακεφαλαιώσασθαι τὰ πάντα ἐν τῷ Χριστῷ "to unite all things in Christ" (there's even an extra ἐν αὐτῷ at the end of the verse which the ESV seems to leave out as redundant)
- Verse 11: ἐν ᾧ καὶ ἐκληρώθημεν "in whom also we have obtained an inheritance"
- Verse 12: ἡμᾶς ... τοὺς προηλπικότας ἐν τῷ Χριστῷ "we ... who were the first to hope in Christ"
- Verse 13: ἐν ᾧ καὶ ὑμεῖς ἀκούσαντες ... ἐν ᾧ καὶ πιστεύσαντες "in whom also you, when you heard ... in whom also, when you believed"
Thus, the rhetorical structure of the passage makes clear that in verse 7, Christ is the one in whom we have redemption. The following prepositional phrase διὰ τοῦ αἵματος αὐτοῦ, "through his blood," serves to make more specific the way in which we have redemption in him: through Christ's blood, shed on the cross (compare Colossians 1:20).
1 Based on the grammatical judgment of the editors who added punctuation to modern editions of the Greek New Testament. There are a couple places where one could perhaps make an argument for putting a sentence break, but the spot in question isn't one of them.
2 For example, later in verse 13, we have ἐν ᾧ καὶ ὑμεῖς ἀκούσαντες τὸν λόγον τῆς ἀληθείας, τὸ εὐαγγέλιον τῆς σωτηρίας ὑμῶν, ἐν ᾧ καὶ πιστεύσαντες ἐσφραγίσθητε τῷ πνεύματι τῆς ἐπαγγελίας τῷ ἁγίῳ. Here, the second instance of ἐν ᾧ could grammatically refer to τὸ εὐαγγέλιον τῆς σωτηρίας ὑμῶν just before it ("the gospel of your salvation, in which [i.e. the gospel] you believed"). However, the parallel ἐν ᾧ καὶ + aorist participle construction signals that both pronouns are tied to the same antecedent (i.e. "Christ," end of verse 12).
3 William J. Larkin, Ephesians: A Handbook on the Greek Text, p 4.