Question: We rented a cottage for the weekend and forgot to check if the fridge had a light that will switch on when we open the door. Could we have asked our three year old child to open and close the fridge on Shabbos?
Answer: The Gemara (Shabbos 120b) writes that it is assur to do a permitted action which will inevitably cause a melacha to be transgressed. This prohibition is known as pesik reisha. Thus, one mustn’t open a fridge door on Shabbos if by doing so it is inevitable that the light will come on, even though the reason they are opening it is to take food out or replace it.
R’ Ovadia Yosef (Yabia Omer 9:OC:108:187) writes that as one benefits from the light going on in the fridge (pesik reisha denicha lei), doing so is assur mideoraisa (See Rambam, Shabbos 1:6). One mustn’t therefore ask a child to open the fridge for them.
While one cannot normally ask a non-Jewish person to do a melacha for them, the Magen Avraham (OC 253:41; 277:7; 314:5) writes that the prohibition of pesik reisha doesn’t apply to them. Thus R’ Moshe Feinstein (Igros Moshe OC 2:68), R’ Ovadia Yosef (Yabia Omer 10:OC:28) and R’ Yehoshua Neuwirth (Shemiras Shabbos Kehilchasa 31:1) write that one can ask a non-Jewish person to open and close the fridge for them. R’ Moshe adds that one may even ask them to remove the bulb if necessary to allow them to open and close the fridge normally afterwards (See Rema OC 276:2), though R’ Neuwirth writes that it is best to hint rather than ask outright.
If the fridge was open, R’ Ovadia Yosef (Yabia Omer, 10:OC:28) writes that one may close it with a shinui (an unusual manner) as shutting the light off in this situation is only miderabanan (See Shulchan Aruch OC 334:27; Mishna Berura 334:84). As there is no constructive benefit in extinguishing the light, closing the door is considered to be pesik reisha delo nicha lei which is assur miderabanan. Alternately, one can ask a child to close the fridge as pesik reisha isn’t forbidden for them (See Mishna Berura 277:15; Avnei Yashpei 1:63).
The Mishna Berura (316:16) writes that there is a machlokes as to whether one can do something when there is a safek, doubt, of there being a pesik reisha. Thus, R’ Yehoshua Neuwirth (Shemiras Shabbos Kehilchasa 10:15) writes that if one doesn’t know whether the light will be turned on or not, there is a machlokes as to whether one can open the fridge themselves or not. Nonetheless, the Mishna Berura writes that we can follow the lenient view.
In conclusion, it is ideal to ask a non-Jewish person to open and close the fridge. As there is a doubt in this scenario as to whether the light would even go off, one can even open the fridge themselves if necessary. One should either ask a child to close it, or close it with a shinui.