The primary reason that traditional Jews don’t drive on the Sabbath is related to Exodus 35:3, discussed immediately above, the prohibition against kindling a fire on the Sabbath. Since the process of ignition is considered to be equivalent to starting a fire—which is also considered a “creative” act, something also prohibited by the rabbis on the Sabbath—to start a car engine would be considered a clear violation of the Sabbath.
As stated on the Ask Moses website:
Turning a key in a car sets the ignition on—which creates a spark—a fire. Not the kind of fire of banging two stones together, but a fire, nevertheless—a human being creating when G-d commands that he rest from all creative acts.
Granted, some of these are so routine and ordinary, with no “work” involved, and don’t seem to involve any genuine creative efforts, but that is the challenge of observing the Shabbat to the letter of the law.[64]
A corollary issue is the Sabbath commandment found in Exodus 16:29 not to go out of one’s “place” on the Sabbath (nasb). This command was given in the context of the gathering of manna: On the sixth day there would be double manna, and it would not rot overnight (in contrast with the other days of the week, in which the manna could not be kept overnight; see Exodus 16:14–26). And so the Israelites did not need to go out and gather manna on the seventh day. Instead it was to be a day of rest (see Exodus 16:27–29).
The ancient rabbis understood this prohibition in a general sense, as opposed to applying it only in terms of not going out to gather manna, making certain loopholes for Sabbath travel within closely proscribed limits (cf. Acts 1:12), but otherwise having the effect of keeping the Jewish people in and around their homes and neighborhoods on the Sabbath. Thus, driving a car would violate this concept in both the spirit and letter of these laws—according to rabbinic interpretation, that is—and for these reasons, traditional Jews do not drive cars on the Sabbath.[65]
Because of this, Orthodox Jews tend to live in close proximity to one another, within walking distance of the synagogue, where they all gather together with their families, thereby putting certain limitations on where exactly they can live. Customs such as this, coupled with the various restrictions that dietary laws place on Orthodox Jews, mean that religious Jews have a number of safeguards against assimilation, along with a fairly strong community base.
In contrast with this, Conservative and Reform Jews do not feel bound by such restrictions, and in the Conservative Jewish community in which I grew up, where the synagogue was about one mile from most of our homes, only the rabbi walked to and from synagogue. As our religious leader, this seemed only appropriate! Some of the men, however, so as to give the appearance of honoring the Sabbath, actually drove to the Sabbath service but parked about one block away, walking the rest of the distance.
It is practices such as these that have caused Orthodox rabbis—in particular, the ultra-Orthodox—to scorn non-Orthodox forms of Judaism (see #1). Some non-Orthodox Jews, however, would point to what, in their minds, constitutes an endless series of loopholes made by the traditional rabbis in order to make their impossibly rigid rules livable. In keeping with this would be the recently developed “KosherLamp” for the Sabbath, discussed earlier (see #14).