The Jews had begun to understand that our Lord was not speaking of sonship according to the flesh, but of manner of life. Scripture often speaks of spiritual fornication, with many gods, and of the soul being prostituted, as it were, by paying worship to false gods. This explains what follows: Then said they to Him, We be not born of fornication; we have one Father, even God.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Tr. xlii. 7.