Rabbi Dr. Jonathan Romain responds to the question: I have always understood that to ‘masser‘ ie to betray a Jew who has committed some crime or other transgression to a non-Jew is a ‘sin’. Is this true in any sense and if so is it based on scripture and are there any conditions surrounding it?
No. The Bible itself is constantly emphasizing the equality of all people, whoever they are. The rights of the stranger are equal to that of a Jew, and they have equal protection before the law. When it declares ‘love your neighbour as yourself’ it does not state ‘your Jewish neighbour’ or ‘your fellow Jew’ but leaves ‘neighbour’ as an open and inclusive term. In later times, when asked if it is worse for a Jew to steal from a Jew or a non-Jew, the rabbis even depart from this sense of strict equality by saying that it is worse to steal from a non-Jew (on the grounds that both acts are wrong, but stealing from non-Jews has the added crime of bringing Judaism into disrepute in the eyes of others). Today, too, we would say that a crime is a crime, and it matters not who is the victim. It would be a betrayal of the strong Jewish sense of justice not to report the person, including a Jew who had acted badly against a non-Jew.
Still, the reluctance to incriminate a Jew to which you refer was a feeling that was held in some periods of Jewish history, particularly in the Middle Ages in Europe when there was tremendous hostility between Jews and society around them. A culture of ‘them and us’ arose in which it was seen as right to protect a fellow Jew from non-Jewish jurisdiction even if he had commited some fault (especially as it was reckoned that a Jew would not receive a fair hearing in the non-Jewish courts anyway). There was also the fear that if a Jew was found guilty, the rest of the local Jewish population would be punished in some way or it might spark a local riot. Some Jews even today may regard the outside world as alien, but whatever the special cases of the past, protecting the guilty is neither right nor justified.