The Mishnah we encounter in today’s daf Yomi (Bava Metzia 83a) is remarkable. It reads:
מתני' השוכר את הפועלים ואמר להם להשכים ולהעריב מקום שנהגו שלא להשכים ושלא להעריב אינו רשאי לכופן
Or, in English:
MISHNAH. ONE WHO ENGAGES LABOURERS AND DEMANDS THAT THEY COMMENCE EARLY OR WORK LATE — WHERE LOCAL USAGE IS NOT TO COMMENCE EARLY OR WORK LATE HE MAY NOT COMPEL THEM.
That is, an employer may not insist, against the local practice, that workers work long hours, say, from dawn to nightfall.
The way that the gemara interprets this, it seems that it is only when he hired the workers without stipulation. Thus, the setama de-gemara (on the same amud) asks that this is obvious, and answers that even if he hired them (presumably without stipulating) and gave them extra money, the workers can reply that that extra money was only to work better, rather than for longer hours. And later (on the next amud), the setama de-gemara asks similarly on a statement by Resh Lakish, and resolves it (maybe just Resh Lakish’s statement, though) in a way that a person can stipulate that it be in accordance with Biblical law, rather than as is the local custom
Tosafot make this explicit. They write:
מתני' השוכר את הפועלי' ואמר להם להשכים ולהעריב. פי' ר"י בששכרן סתמא ואמר להם אחר שהשכירן כבר להשכים ולהעריב אבל אם התנה מעיקרא הכל לפי תנאו:
“The Ri exlpains that this is where he hired them without stipulation, and only after he had already hired them, tells them to get up early and work late. But if he stipulated at the start, all will be in accordance with his stipulation.”
I agree that, based on the give and take of the setama degemara, this is a very sensible reading of the gemara.
However, two thoughts. First, when the gemara asks that this is obvious, that all unstipulated hiring would be in accordance with local standards, it could be that it is only obvious because the gemara has already internalized the legal structure and principle upon which the Mishna was trying to expound. That is, one might have thought that one who hires a worker effectively has bought their labor for the day, and so whatever the local culture, he has bought the labor and can instruct them as he sees fit. Therefore it is teaching us that the local culture defines the expectations by which they have hired themselves out, and so such is legally binding, even if he didn’t give them extra money.
Second, I suspect that the Mishna is teaching us an even more remarkable ruling, against Tosafot. That is, even if the owner explicitly stipulates with them at the outset that they work longer hours, against local custom, as a takanat chachamim, such a stipulation has no force. And such a law would not be peshita, obvious.
Why make such a law, to protect the worker? Why shouldn’t we take a libertarian, anti-union position, that the worker and employer are free to enter into any binding contract they choose to enter? That if the worker wants to work these longer hours, either because he will get more money, or because he will thereby be the worker who finds employment, he may do so?
Because there is an imbalance of power. There is plenty of labor available, and the employer has leverage to demand all sorts of wages or all sorts of working hours. If this laborer doesn’t agree, he could just hire another laborer. The laborer wants to eat, and if he is allowed to enter into negotiation for such quality-of-life-affecting conditions, he and all other laborers will end up with miserable lives. This is what happened during the Industrial Revolution, with horrible working conditions, low pay, child labor, and so on.
For tikkun olam, Chazal took such a negotiation out of the hands of the employer and laborer. Even if they explicitly stipulated against it, the local custom, which ensures quality of life, prevails. Minhag is oker halacha. אמר רב הושעיה זאת אומרת המנהג מבטל את ההלכה
For slight support for this, the position of Resh Lakish, that working come to work on their employer’s time and come home on their own time, seems to be understood by the Bavli as Biblical law, able to be stipulated against, or only in force when there is no existing custom. The parallel Yerushalmi has a statement by Rabbi Ami that casts it as a tenei bet din, in order to accomplish a specific social goal:
רבי אמי רב יהודה תניי בית דין הוא שתהא השכמה של פועלין והערבה של בעל הבית ומאי טעמא תשת חשך ויהי לילה הכפירים שואגים לטרף תתן להם ילקוטון תזרח השמש יאספון יצא אדם לפעלו ערבית בין השכמה בין הערבה משל בעל הבית עד איכן עד כדי למלאות לו חבית מים ולצלות לו דגה ולהדליק לו נר