Reprinted with permission from The Theory and Practice of Welcoming Converts to Judaism (The Edwin Mellen Press, Ltd.).
One of the difficulties about considering conversion in the talmudic period was that the biblical terminology used to discuss the subject was redefined by the rabbis. For the rabbis, for instance, a ger [a “stranger” in the Bible] specifically meant a convert to Judaism.
Categories of Gerim
The rabbis made a distinction between two types of gerim. A ger toshav, or settler convert, also called a ger ha-sha’ar (or proselyte of the gate, as in Exodus 20:10), was a resident alien given permission to live in land controlled by Jews if he or she did not worship other gods or engage in idolatry of any kind or blaspheme God. The ger toshav agreed in the presence of three scholars to follow these Jewish principles. In addition, a ger toshav had to observe the Noahide laws [seven laws considered binding on all humam beings, including prohibition of idolatry and murder]. The ger toshav did not have to perform work on the Sabbath, but was not required to join in worship or perform specifically Jewish religious commandments. Maimonides called them righteous gentiles. They were clearly not full converts to Judaism.
The second category of gerim was the ger tzedek, a righteous proselyte, one who converted for the sake of religious truth and not for any other motive. (Such a ger was also called a ger emet, a true proselyte, or a ger ben b’rit, a proselyte who is a child of the covenant.) These gerim didn’t just follow the principles of Judaism, but also its rituals and practices. They are mentioned in the 13th blessing of the Amidah [the major prayer in Jewish liturgy].
Some people, the gerurim, converted to Judaism for nonreligious reasons such as marriage or a perceived economic or other advantage. Such proselytes (including, for example, the Gibeonites, who became Jewish by a trick to avoid destruction, and those who had been forcibly converted) were considered to be fully Jewish.