John Chrysostom, on Rom 5:12

“Wherefore as by one man sin entered into this world, and by sin death; and so death passed upon all men, in whom all have sinned.”

“As the best physicians always take great pains to discover the source of diseases, and go to the very fountain of the mischief, so doth the blessed Paul also. Hence after having said that we were justified, and having shown it from the Patriarch, and from the Spirit, and from the dying of Christ (for He would not have died unless He intended to justify), he next confirms from other sources also what he had at such length demonstrated. And he confirms his proposition from things opposite, that is, from death and sin. How, and in what way? He enquires whence death came in, and how it prevailed. How then did death come in and prevail? "Through the sin of one." But what means, "for that all have sinned?" This; he having once fallen, even they that had not eaten of the tree did from him, all of them, become mortal.”

Imported from an open dataset — not yet checked against the printed edition.