Question: In our apartment building, the lights in the stairwell go on automatically by means of a motion sensor activated when someone enters. Is it permissible to enter the stairwell on Shabbat?
Answer: The Gemara (Shabbat 120b) states, “The Torah states, “You shall not perform any work,” performing work is forbidden but causative work is permitted.” This means that the Torah only prohibits performing work on Shabbat in the regular manner it is performed. For instance, watering a field by hand is a Torah prohibition on Shabbat. However, any work that one does not perform in a direct manner and is only an indirect effect is not considered the regular manner of performing the work, such as, if one pours some water inside one’s home to clean it and the water flows on their own through the building’s piping to the building’s garden; this cannot be considered a “direct method of work”. The Poskim disagree if an indirect form of work (causative) may be performed without hindrance even when there is no financial loss or if one should not act leniently in this regard.
Regarding turning on electricity on Shabbat, this is a Torah prohibition since the electricity is a form of combustion and the way lightbulbs work in our times is that they are turned on by flicking a switch and doing so creates an electrical circuit and causes the filament in the lightbulb to combust. On the other hand, there is room to claim that lights turned on by means of a sensor cannot be considered an “act of combustion” and is merely an “indirect” or “causative” act.
Approximately ten years ago, we posed a similar question to Maran Rabbeinu Ovadia Yosef zt”l, however, there the individual said that if he would not be permitted to enter the stairwell on Shabbat, he would have to move to another neighborhood and the ordeal would cause him much stress and aggravation. He added that he was not the only one who had to deal with this problem and that there were many Jews who lived in such apartment buildings and they have no other way to go up to their apartments. Nonetheless, Maran zt”l ruled that one may not act leniently, for the turning on of a light by means of a motion sensor is not considered an “indirect” act since this is the regular way these lights are activated that when someone enters the room, the sensors immediately recognize the motion and the light turns on. As such, this would constitute a true Torah prohibition (when dealing with incandescent lightbulbs). Although we explained to Maran zt”l that this issue greatly inconveniences many people living in such apartment buildings in Paris where the law dictates that buildings must be equipped with motion-activated lights as opposed to manual ones, Maran nevertheless repeated that there was no room for leniency regarding this matter and if need be, these individuals should relocate elsewhere and that Hashem would grant them success in building their new homes.
Similarly, the great Rishon Le’Zion, Hagaon Harav Yitzchak Yosef Shlit”a, rules stringently on this matter and writes that he posed the same question to Maran zt”l approximately twenty years ago and he offered the claim of those who wished to rule leniently which was that this act was not being performed by hand and it should therefore be classified as an “indirect” action. However, Maran zt”l refuted this idea and provided proofs as well and ruled that entering such a building is forbidden on Shabbat. (Nevertheless, the Rishon Le’Zion concludes that when there is absolutely no other alternative, there is some room for leniency based on the commentary of the Rashba on Shabbat 107a. Thus, one who does not have any other alternative should consult with a prominent Posek regarding how to proceed.)
Summary: It is forbidden a room equipped with motion sensors which turn on the lights on Shabbat.
In the following Halacha, we shall discuss some other laws related to this matter.
