Bone of His Bone, Flesh of His Flesh

Paul uses the Marriage metaphor to describe Christ's relationship to His Church. He loves the Church as a Husband ought to love his wife.

He has treated us as His own flesh and bone. He sacrificed his own Body at Calvary for the sake of His body the Church.

Paul compares Christ's espousal to the Church with the very first marriage between Adam and Eve. The First Adam tried to shift his own moral guiltiness onto his wife Eve. The Last Adam shifted the Church's moral guiltiness onto Himself at the cross.

He has done for His people the thing they most desperately needed: he has taken on himself the duty to discharge their debt to divine justice, interposing His very body between His Church and the Wrath of God.

Christ's relation to his Church is no mere legal fiction - His interest in us is intensely personal, which is a reason why Paul uses the marriage metaphor to describe it.