Epictetus in Discourses 2.9 (c. 100 CE) speaks of Jews and baptism.  In the context of the need of consistency between doing and thinking:

When we see a man trimming between two faiths we are wont to say, ‘He is no Jew, but is acting a part’, but when he adopts the attitude of mind of him who is baptized and has made his choice, then he is not only called a Jew but is a Jew indeed.  So we also are but conterfeit ‘baptists’, Jews in name only, but really something else, with no feeling for reason, far from acting on the principles we talk of, though we pride ourselves on them as though we knew them.