Christ and the Church are one Christ.
Thus, at times, Christ is intimated in the Scriptures so that you might understand the Word as equal to the Father. At other times, so that you might understand Him as mediator; when the Word became flesh to dwell among us; when the Only Begotten, through whom all things were made, did not consider equality with God something to be grasped, but emptied Himself, taking the form of a servant, and became obedient to the point of death, even death on a cross. Yet at other times, so that you might understand the head and the body, as the Apostle himself most clearly explains what was said about the man and woman in Genesis: They shall be, he said, two in one flesh. Look at him explaining it so that we do not seem to dare say something based on our own conjectures. For, he said, they shall be two in one flesh; and he added: This is a great mystery. And lest anyone still think that this refers to the man and the woman according to the natural coupling of both sexes and bodily mixture: But I am speaking, he said, of Christ and the Church. According to this, therefore, what is taken to mean Christ and the Church when it was said: They shall be two in one flesh; no longer two, but one flesh. And as the bridegroom and the bride, so the head and the body: because the head of the woman is the man. Whether, therefore, I say the head and body, or I say the bridegroom and bride; understand them as one. And thus the same Apostle, while he was still Saul, heard: Saul, Saul, why do you persecute me? because the body is joined to the head. And when he already as a preacher of Christ suffered from others the things he had himself done as a persecutor: To fill up, he said, what is lacking in Christ's afflictions in my flesh; showing that what he suffered pertained to Christ's afflictions. This cannot be understood with regard to the head, which now in heaven suffers nothing of the sort; but with regard to the body, that is, the Church; which body, with its head, is one Christ.
The bride of Christ should act to be without spot or wrinkle.
Therefore, present yourselves as a body worthy of such a head, as a spouse worthy of such a groom. That head cannot have anything other but a fitting body; nor can such a great man have anything other but a worthy wife. So that He might present to Himself, as it is said, a glorious Church, not having spot or wrinkle, or any such thing. This is the bride of Christ, not having spot or wrinkle. Do you not want to have a spot? Do what is written: Be washed, be clean, take away wickedness from your hearts. Do you not want to have a wrinkle? Be stretched out on the cross. For it is not only necessary to be washed, but also to be stretched out, so that you may be without spot or wrinkle. For sins are taken away through washing; through stretching out, the desire for the future age is realized, for which Christ was crucified. Listen to Paul himself being washed: Not by works of righteousness which we have done, he says, but according to His mercy He saved us, by the washing of regeneration. Listen to the same one being stretched out: Forgetting what lies behind, he says, and reaching forward to what lies ahead, I press on toward the goal for the prize of the upward call of God in Christ Jesus.