Hello Rav, how are you?
I currently work in the office of a non-kosher Japanese restaurant group and, at the same time, I also serve occasionally as a mashgiach. In this capacity, I work under different rabbanim and in various settings, usually with people who are very strict in their observance of Halacha, often even more stringent than what is strictly required.
I recall that in 2020 you answered a question permitting the consumption of sashimi under certain circumstances. Based on that response, I have a few practical questions.
For example: if the knife used to cut the sashimi had previously been used to cut something hot, would that pose a halachic issue? And regarding the plate on which the sashimi is served—if it is made of a material that absorbs taste and had been previously used, then washed and reused—would there be any restriction on eating from it?
In addition, I would appreciate clarification regarding the issue of mar’it ayin. Even if there is halachic room for leniency, how should one deal with the concern that others may see me eating in a non-kosher restaurant and judge negatively, without knowing the halachic background or permissions involved?
If possible, I would also be grateful if the Rav could indicate the halachic sources for these issues, such as references in the Shulchan Aruch, Rambam, or other relevant poskim.
Thank you very much in advance for your time and guidance.
Thank you for your thoughtful and sincere question. It is clear that you are trying to navigate these issues honestly, both professionally and halachically, and that itself deserves respect.
Before addressing the technical points, I want to clarify something implicit in your opening remarks. You note that you often work under rabbanim and in environments that are “very strict,” sometimes more stringent than what is strictly required by Halacha. I fully understand that, as an employee or mashgiach, one must follow the standards imposed by the supervising authority. At the same time, it is important for one’s own clarity to remember that extra stringencies are not inherently virtuous. The Gemara already cautions that one who exempts himself from a permitted matter and nonetheless forbids it upon himself is called a hedyot, and this idea appears in many places throughout Chazal. Halacha values precision and honesty, not exaggeration or fear-based additions. This is not meant as criticism, only as an important personal reminder when thinking about these issues.
Knives used for sashimi
Regarding the knife used to cut sashimi: there is no halachic concern here. In normal contemporary kitchen practice, knives are not used on a kli rishon on the fire. That simply is not how knives are used today. Even if a knife were previously used on hot food, by the time it is used for sashimi everything involved is cold: the knife is cold, the fish is cold, and there is no heat transfer that would create absorption issues.
Beyond the technical halachic framework, there is also the simple reality of experience. People eat sashimi regularly. No one has ever tasted salmon in their tuna, or tuna in their salmon, due to a knife. If that were happening, the restaurant would not survive. Halacha does not operate in a vacuum detached from reality.
Plates and absorption
The same applies to the plate. Plates in restaurants are not used as kli rishon; they are, at most, kli sheni. Furthermore, modern plates are glazed, and glazed ceramic or glass does not absorb taste in a halachically meaningful way. Again, this is evident in real life: when you eat in a restaurant, do you ever taste lobster, crab, or any other food that was supposedly “absorbed” into the plate? Of course not. This concern is theoretical to the point of irrelevance.
Mar’it ayin
As for mar’it ayin, this concept is frequently misunderstood and greatly overextended. Mar’it ayin applies only in situations explicitly identified by Chazal (and possibly early Rishonim), where an observer could only reasonably conclude that a prohibition is being violated.
Walking into a restaurant does not meet that standard. If it did, one could not walk into a 7-Eleven, board an airplane, or enter any public place that sells non-kosher food. Restaurants have always existed, and Jews have always entered them to eat permitted items. Every restaurant today sells coffee. Many sell fish, vegetables, salads, or other plainly permissible items. Even if someone sees you eating in a Japanese restaurant, why should they assume you are eating shrimp rather than tuna or salmon?
Mar’it ayin is not triggered by the fact that some people are judgmental or uninformed. That is their issue to work on, not yours. The only classic case where mar’it ayin applies is when no alternative explanation exists — for example, entering a brothel, where the assumption of prohibited activity is essentially unavoidable unless clearly contradicted. A restaurant is nothing like that.
Creating new categories of mar’it ayin based on communal suspicion or social pressure would make normal life impossible and was never the intent of Halacha.
Sources
Much of this follows directly from basic principles found throughout the Shulchan Aruch regarding kli rishon and kli sheni, absorption, and cold foods, as well as the Gemara’s clear limitations on mar’it ayin. I am currently preparing a more comprehensive article on taruvot (mixtures), where many of these issues — knives, utensils, absorption, and exaggerated stringencies — will be addressed systematically, with sources. When that is ready, it will hopefully provide a more detailed framework for these and similar questions.
In the meantime, your instinct to ask and clarify is correct. Halacha is meant to be lived honestly, thoughtfully, and without unnecessary fear.