Bechoros 29a: The Sages permitted Illa of Yavneh to charge a fee for checking a firstborn animal for blemishes (in the absence of the Beis Hamikdash, a firstborn is permitted to eat only if it has a blemish). He charged four issar for a sheep or goat and six issar for a cow, regardless of whether he declared it blemished or unblemished.
Shulchan Aruch Yoreh Deah 18:18: The shochet, who inspects the animal for defects after slaughter, must charge the same fee whether the animal turns out to be kosher or treif, lest he come to rule leniently in order to make more money. For this reason, it is customary in some places that no butcher slaughters and checks his own animals, but rather he has it done by the community shochet.
בכורות כט. כאילא ביבנה שהתירו לו חכמים להיות נוטל ארבע איסרות לבהמה דקה וששה לגסה בין תם ובין בעל מום.
שו”ע יו”ד י”ח סי”ח הטבח צריך שיטול שכר מן הטרפות כמו מן הכשרות, הגה שלא יבא להקל להכשיר כדי לקבל שכרו מן הכשרות ולכן נהגו בקצת מקומות שאין אדם שוחט ובודק לעצמו אלא אותן הממונים מן הקהל.
Once, the kosher bakery owners of Antwerp met together and decided to stop giving the keys of their bakeries to the mashgichim. [Presumably, they didn’t want to have to wait for the mashgiach to come and open the bakery in the morning.] The Rav Hamachshir, Rabbi Chaim Kreiswirth, did not back down. Taking several of the heads of the kehillah with him, he went around on Shabbos to all the shuls and announced that until further notice, he was removing his hashgacha from all the bakeries, with no exceptions. He added that if anyone wanted bread, he permitted them to eat “pas paltar” – kosher bread baked by a non-Jewish baker.
The following Friday, an oven was set up in the courtyard of the shul, and the Rav himself, together with the heads of the kehillah, baked challah for Shabbos, for those who wished to be strict and not eat pas paltar on Shabbos.
One of the bakery owners was a member of a prominent Chassidishe kehillah, and an influential member of that Chassidus announced in shul, “So-and-so is totally reliable and I will continue to eat his products, with or without hashgacha!” And to show he meant what he said, the next morning he brought cakes and other baked goods from that bakery to shul.
Not long afterward, this man contracted a stomach illness and died. After that, no one dared defy Rav Kreiswirth’s authority in Antwerp.
Source: Mayim Chaim, page 144
[The above quotation from Yoreh Deah 18 explains why we need hashgacha in general, rather than relying on a business owner who is a shomer Torah. But this story deals with a different aspect of hashgacha: how to handle a store where the labor is done by non-Jews. Does the mashgiach have to be present all the time, or can he make occasional, unexpected visits (יוצא ונכנס)? Rav Kreiswirth held that in a bakery, the mashgiach must be present all the time, and the only way to enforce that is by giving him the only key to the bakery.
Why wasn’t he willing to rely on occasional visits? After all, the Mishnah (Avodah Zarah 61a) says that יוצא ונכנס works, and it’s brought in Shulchan Aruch. The answer may be that occasional visits make workers afraid to do something that takes a while, such as unloading non-kosher ingredients and using them. But in a Jewish-owned bakery, which needs to be pas yisroel (the heter of pas paltar only applies when the owner is a non-Jew, as the Shach 112:7 says), lighting the oven takes only a second. If the workers were to open the bakery in the morning and find the pilot light out, they might relight it, and when the mashgiach arrives half an hour later, he would never know that anything had gone wrong.
This point is made by R’ Moshe in his teshuva requiring a mashgiach temidi on fish (Igros Moshe Yoreh Deah 3:8). These fish were sold without the scales, so the customer would have no way of knowing if they were kosher fish. He writes that if the skinning were done by hand, the mashgiach could walk in and out, and that would be enough to deter the workers from skinning a non-kosher fish lest the mashgiach walk in and catch him in the middle. But the skinning is done very fast by a machine, and it would be easy to get it done in that moment when the mashgiach’s back is turned. Therefore the mashgiach must check every single fish.]
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