The commandments in the Torah were divided into two groups: mishpatim, and hukkim.
Mishpatim are the reasonable and self-evident laws, such as the prohibitions against murder and adultery.
Hukkim represent those commandments impenetrable to reason.
Prohibition Against Eating Fish and Meat Together
The Gemara relates: There was a certain fish that was roasted together with meat, Rava of Parzikiyya prohibited it from being eaten with kutaḥ, due to the meat flavor absorbed in the fish. Mar bar Rav Ashi said: Even to merely eat it with salt is also prohibited because meat that is roasted or cooked with fish is bad for odor, meaning it causes bad breath, and for something else, i.e., leprosy. Therefore, one should avoid eating it due to the danger involved.
Fish + Meat = Leprosy
WHAT?????!!!
The first place in rabbinic literature where we see an outright prohibition against eating fish and meat together is in the Shulchan Aruch, where Rabbi Joseph Caro writes that one must abstain from doing so because that combination causes a danger to one’s health (Yoreh Deah 116:2-3).
Caro is clear that the mandated separation between meat and fish is made out of concern for medical risk, not because the combination is explicitly prohibited by the Torah.
As a result of this ruling in the Shulchan Aruch, halacha (Jewish law) prohibits cooking fish and meat together, or serving them together in one dish.
Some rabbinic authorities require the washing of hands, and others mandate a drink of water, or a piece of bread to cleanse the palate between the two courses, but there’s no need to wait several hours between salmon and steak.
Is this law still followed today?
In Orthodox communities, the separation between meat and fish is generally still upheld, under the logic that the standards for safety made by Rabbi Caro have not changed. However, the Conservative Movement’s Committee on Jewish Law and Standards has overturned the prohibition against cooking and eating meat and fish together. This reversal is based on the idea that the prohibition originally came from a specific desire to avoid getting tzaraat. Because tzaraat is not a problem in our times, it’s no longer necessary to go to great length to avoid catching it.
What can be used to establish an eruv?
If one gave the eiruv to a trained elephant, and it brought it to the place where he wanted the eiruv deposited, or if he gave it to a monkey, and it brought it to the proper location, it is not a valid eiruv. But if he told another person to receive it from the animal, it is a valid eiruv. The Gemara asks: But perhaps the animal will not bring the eiruv to the person appointed to receive it? Rav Ḥisda said: The baraita is referring to a case where the person sending the eiruv stands and watches it from afar until it reaches the person designated to receive the eiruv. The Gemara asks further: But perhaps the person appointed to receive the eiruv will not accept it from the elephant or monkey. Rav Yeḥiel said: There is a legal presumption that an agent fulfills his agency.
Where and With What May a Sukkah be Built?
The mishna continues: Or if one establishes his sukka atop a camel, the sukka is fit. The Gemara asks: Who is the tanna of the mishna? It is in accordance with the opinion of Rabbi Meir, as it is taught in a baraita: In the case of one who establishes his sukka atop an animal, Rabbi Meir deems it fit and Rabbi Yehuda deems it unfit.
The Gemara asks: What is the rationale for the opinion of Rabbi Meir, who rules that an animal is unfit for use as a partition in areas of halakha where a partition is required? Abaye said: It is due to the concern lest the animal die, leaving the sukka without a wall. Rabbi Zeira said: It is due to the concern lest it flee. The Gemara explains the practical halakhic differences between the two opinions.
In the case where one established a wall with a tied elephant, everyone agrees that the sukka is fit, as even if it dies and falls, its carcass still has a height of ten handbreadths and is fit for the wall of a sukka. Where they disagree is in the case of an elephant that is not tied. According to the one who said: It is due to the concern lest the animal die, we are not concerned in this case, as the carcass would remain a fit wall. According to the one who said: It is due to a decree lest it flee, we remain concerned. The Gemara asks: According to the one who said: It is due to a decree lest it die, let us also be concerned lest it flee, as that too is a reasonable concern. Rather, this is the explanation:
In the case where one established a wall with an elephant that is not tied, everyone agrees that the sukka is unfit lest it flee. Where they disagree is in the case of a tied animal. According to the one who said: It is due to a decree lest the animal die, we are concerned, as although it cannot flee, it might die, and the carcass of a typical animal is not ten handbreadths high. And according to the one who said: It is due to a decree lest it flee, we are not concerned. The Gemara asks: And according to the one who said: It is due to a decree lest it flee, let us also be concerned lest it die. The Gemara answers: That is not a concern because death is not common. The Sages do not issue decrees with regard to uncommon circumstances.
The Gemara asks: But according to all opinions, isn’t there the space between its legs, which is like a breach in a wall? How can one establish a partition whose breached segment exceeds its standing segment?
The Gemara answers: He establishes a partition for it by filling the gaps with hard palm leaves and laurel leaves, sealing the breach. The Gemara asks further: And even though there is no concern lest the animal die, perhaps it will crouch, leaving a wall that is less than ten handbreadths? The Gemara answers: It is referring to a case where the animal is tied with ropes from above so that it cannot crouch. Based on that explanation, the Gemara asks: And according to the one who said: It is due to a decree lest it die, there is also no concern since it is tied with ropes from above. Even if the animal died, it would remain in place as a fit partition. The Gemara answers: Sometimes the ten-handbreadth wall consists of the animal that is a bit higher than seven handbreadths established adjacent to the roofing, less than three handbreadths away.
(א) דיני הכנסת שבת. ובו ב סעיפים:
מצוה לרחוץ: הגה כל גופו ואם א"א לו ירחץ (טור) פניו ידיו ורגליו בחמין בע"ש ומצוה לחוף הראש ולגלח הצפרנים בע"ש: הגה ואם היו שערות ראשו גדולות מצוה לגלחן (א"ז פ' אלו מגלחין) וכשנוטל צפרניו לא יטול אותן כסדרן ויתחיל בשמאל בקמיצה ובימין באצבע וסי' לזה דבהג"א בשמאל ובדאג"ה בימין (אבודרהם בספר המוסר):
(1) 1. Laws Governing [Preparations for] the Onset of Shabbos, 2 Seifim: It is a mitzvah to wash one’s head and trim one’s nails every Friday. RAMA: If one’s hair [has grown] too long, it is a mitzvah for him to cut it. And when one trims one's nails one should not grab hold of them in order. One should begin trimming the nails of his left hand with [those of] the kamitzah, (i.e., the fourth finger, the one next to the pinky). On the right hand, [one should start] with the index finger, the second finger, the one next to the thumb. Thus, a memory cue for the order is בדאג"ה (2, 4, 1, 3, 5) on the right hand and דבהג"א (4, 2, 5, 3, 1) on the left. (Avudraham in the Sefer HaMussar)
- When cutting our nails, we don't cut the nails on 2 consecutive digits one after the other, rather we skip every other one and then go back (e.g. we'll cut the nails of the thumb, middle finger, pinky, index finger and the ring finger) (Orach Chayim 260:1).
Jews and Shoes
(ד) ינעול מנעל ימין תחלה ולא יקשרנו ואח"כ ינעול של שמאל ויקשרנו ויחזור ויקשור של ימין: הגה ובמנעלי' שלנו שאין להם קשירה ינעול של ימין תחל' (תוס' פ' במה אשה דס"א):
(4) One should put on the right shoe first and not fasten it, then after that put on the left one and fasten it, and return and fasten the right one. Rem"a: And in the case of our shoes which do not have a fastening, one puts the right one on first. (Tosafot)
Laws of Halitzah
The brother could also opt to release her to marry someone else. This is the ceremony of halitzah. The widow and her brother-in-law appear before a rabbinical court, a beth din, consisting of five members. The brother-in-law wears on his right foot what is known as the halitzah shoe. This special shoe is made from the skin of a kosher animal and consists of two pieces sown together with leather threads. It must not contain metal and is designed like a moccasin with long straps.
The widow declares that her brother-in-law refuses to marry her, and he confirms it as directed in Deuteronomy (25:7 and 9). She then places her left hand on his calf, undoes the laces with her right hand, removes the shoe from his foot, throws it to the ground, and spits on the ground in front of him. The beth din then recites the formula releasing all obligations.
The shoe is a symbol of the transaction.
The Kabbalists describe the body as "the shoe of the soul." Just as shoes protect feet from the dirt, so too does the soul require the body as a shoe to protect it during its journey in the physical world.
https://www.chabad.org/library/article_cdo/aid/407510/jewish/Jews-and-Shoes.htm
The rationale for what was called a levirate marriage was to continue the name, the assets and the soul of the deceased brother through the subsequent marriage and children
Shiluach haken (Hebrew: שילוח הקן, "sending-away the nest") is the Jewish law derived from the Torah that enjoins one to scare away the mother bird before taking her young or her eggs. This only applies to Kosher birds in the wild. The Torah promises longevity to someone who performs this commandment. It is also understood as a sign of compassion.
According to the "rationalist" approach, the purpose of the commandment is compassion: either to spare the mother bird the distress of seeing its eggs taken, or to limit the greed inherent in killing animals for one's use
This is one of the few individual commandments for which a specific reward is promised in the text.