Acts 16:3

and circumcised him It must be remembered that the decree of the synod of Jerusalem only related to the exemption of Gentiles from circumcision. It was a very different thing for a Jew to consent to become a fellow-worshipper in the Christian churches with a Gentile who remained uncircumcised, and to tolerate, at this time, the non-observance of the rite by one who was counted for a Jew. For by the Rabbinical code the child of a Jewish mother was reckoned as a Jew (T. J. Jebamoth, ii. 6). It was because of this prejudice that Timothy was circumcised. It could be no offence to the Gentiles, and would render the labours of Timothy more acceptable to the Jews. Because he was the child of a mixed marriage the rite had been unobserved, and so long as he did not come forward as a teacher, there would be no need felt that it should be enforced, and there would be doubtless many others of a like class. But when he was to take a share in the missionary labours of St Paul all this was altered. He would at once have been met with the objection from the Jews, that he who had been but a bad Jew was not likely to guide others right as a Christian teacher. That St Paul saw no inconsistency in what was done in this matter is clear, for the narrative of St Luke tells us in the next verse that to the churches to which they went forth he delivered the decrees of the synod at Jerusalem.