Epistle to Diognetus

But as to their scrupulosity concerning meats, and their superstition as respects the Sabbaths, and their boasting about circumcision, and their fancies about fasting and the new moons, which are utterly ridiculous and unworthy of notice—I do not think that you require to learn anything from me. For, to accept some of those things which have been formed by God for the use of men as properly formed, and to reject others as useless and redundant—how can this be lawful? And to speak falsely of God, as if He forbade us to do what is good on the Sabbath-days—how is not this impious?

And to glory in the circumcision of the flesh as a proof of election, and as if, on account of it, they were specially beloved by God—how is it not a subject of ridicule? And as to their observing months and days, as if waiting upon the stars and the moon, and their distributing, according to their own tendencies, the appointments of God, and the vicissitudes of the seasons, some for festivities, and others for mourning—who would deem this a part of divine worship, and not much rather a manifestation of folly?

I suppose, then, you are sufficiently convinced that the Christians properly abstain from the vanity and error common [to both Jews and Gentiles], and from the busybody spirit and vain boasting of the Jews; but you must not hope to learn the mystery of their peculiar mode of worshipping God from any mortal.