It is the Spirit that speaketh, whereas he understandeth carnally; he knew of no birth save one, that from Adam and Eve; from God and the Church he knows of none. But do thou so understand the birth of the Spirit, as Nicodemus did the birth of the flesh; for as the entrance into the womb cannot be repeated, so neither can baptism.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Tr. xi. c. 6