12 If, then, there is one wanting to fulfill, whence does he not fulfill? Because born with the heritage of sin and death. Born of Adam, he drew with him that which was there conceived. The first man fell, and all who were born of him from him derived the concupiscence of the flesh. It was needful that another man should be born who derived no concupiscence. A man and a man: a man to death and a man to life. Thus says the apostle: “Since, indeed, by man death, by man also the resurrection of the dead.”
By which man death, and by which man the resurrection of the dead? Do not make haste: he goes on to say, “For as in Adam all die, so also in Christ shall all be made alive.” Who belong to Adam? All who are born of Adam. Who to Christ? All who were born through Christ. Wherefore all in sin? Because no one was born except through Adam. But that they were born of Adam was of necessity, arising from damnation; to be born through Christ is of will and grace. Men are not compelled to be born through Christ: not because they wished were they born of Adam.
All, however, who are of Adam are sinners with sin: all who are through Christ are justified, and just not in themselves, but in Him. For in themselves, if you should ask, they belong to Adam: in Him, if you should ask, they belong to Christ. Wherefore? Because He, the Head, our Lord Jesus Christ, did not come with the heritage of sin; but He came nevertheless with mortal flesh.
Source: Tractates on the Gospel of John (New Advent)