The Epistle to Diogentus

Moreover I do not suppose that youmeed to learn from me that, after all, their scruples about food and superstition about the Sabbath, and their pride in circumcision and the sham of their fasting and feast of the new moon, are ridiculous and unworthy of any argument.

For how can it be anything but unlawful to receive some of the things created by God for the use of man as if well created, and to reject others as if useless and superfluous?

And what can it be but impious falsely to accuse God of forbidding that a good deed should be done on the Sabbath day?

And what does it deserve but ridicule to be proud of the mutilation of the flesh as a proof of election, as if

And their attention to the stars and moon, for the observance of months and days, and for their arbitrary distinctions between the changing seasons ordained by God, making some into feasts, and others into occasions of mourning;—who would regard this as a proof of piety, and not much more of foolishness?

So then I think that you have learnt sufficiently that the Christians do rightly in abstaining from the general silliness and deceit and fussiness and pride of the Jews. But do not suppose that you can learn from man the mystery of the Christians’ own religion.