In him we have redemption through his blood, the forgiveness of our trespasses, according to the riches of his grace
Concerning family and blood, Jerome Neyrey says,
…the most important institution in antiquity was the family, which conveyed to its members their personal identity and social standing. … all the members of the family share in its reputation: all rejoice in its honor and all share in its shame. Honor, then, is symbolized by family blood” (Neyrey, p. 21).
Remember that in Ephesians 1:5 we were “predestined for adoption …” From the perspective of honor and shame, adoption into God’s family makes more sense when understood as a transaction secured by family blood. Jesus, the Son of God, shed his blood for the forgiveness of our trespasses. Our trespasses, our sins, are what separate us from God. It is the source of our inescapable guilt and total shame before God.
But “we have redemption through his blood for the forgiveness of our trespasses according to the riches of his grace.” This then becomes the base of our new identity, having our guilt and shame removed to secure our new righteousness and honor before God.