Excerpted with permission from "Conversion According to Halakhah" (Vol. 3, pp. 59-68, YD 268), a responsum of the Masorti (Conservative) movement in Israel. A responsum is a rabbinical opinion on a contemporary legal question, based on earlier Jewish texts. This section of the responsum explicates the traditional requirement for conversion, kabbalat ol hamitzvot (acceptance of the yoke of the commandments), for today’s Masorti Jews. This Masorti interpretation differs from the stricter view of many Orthodox rabbis that kabbalat ol hamitzvot requires a convert to commit to the performance of all applicable Jewish commandments.
Firstly, one notes, in this context, that the phrase "accepting the yoke of the commandments" does not appear in the Talmudic sources, though, to be sure, there is a statement that might be considered as such. In a Baraita (Yevamot 47 a-b) we read: "We inform the candidate for conversion of some of the easier and some of the more severe commandments, but we do not enlarge on this matter and do not go into detail."
Maimonides (Hilkhot Issurey Biah 13:2) writes in a similar vein and goes on to add: "We do not go into detail." In the same chapter in his Code (13:7), Maimonides writes that if for any reason this phase of conversion was omitted, the fact does not invalidate the conversion.
The Shulhan Arukh (Yore Deah sec. 268) repeats Maimonides almost verbatim but adds that ab initio "accepting the yoke of the commandments" is indispensable but if the convert nevertheless married a Jewess without doing so, his conversion is not invalidated.
One raises the following very practical question in the light of present-day circumstances, and especially in the light of what the Talmud says on the subject. What if the court (beit din) that convened to accept a candidate for conversion is aware that after conversion the person involved will not observe some or most of the commandments, may he (or she) be accepted? Does not the Talmud (Bekhorot 30b) declare: "A Gentile who comes to accept the Torah (conversion) except for one item (in the Torah), we do not accept him?"