Gilui (uncovered drinks), meat and fish (בשר ודג) and kinuach ve-hadacha, human sweat, the great principle סכנתא חמירא מאיסורא and שומר נפשו ירחק, bal teshaktzu and the mesukenet animal (Shulchan Aruch, Yoreh De'ah 116 — 7 se'ifim)
יִזָּהֵר מִכָּל דְּבָרִים הַמְּבִיאִים לִידֵי סַכָּנָה, כִּי סַכַּנְתָּא חֲמִירָא מֵאִיסּוּרָא, וְיֵשׁ לִזָּהֵר בְּסַפֵק סַכָּנָה טְפֵי מִסְּפֵק אִיסּוּר. וְעַל כֵּן אָסְרוּ לֶאֱכֹל וְלִשְׁתּוֹת מִדְּבָרִים שֶׁיֵּשׁ בָּהֶם חֲשַׁשׁ סַכָּנָה.
One should beware of all things that lead to danger, for danger is graver than prohibition (סכנתא חמירא מאיסורא), and one must be more careful of a doubt of danger than a doubt of prohibition. Therefore they forbade eating and drinking things in which there is a risk of danger.
Shulchan Aruch, Yoreh De'ah 116:5 (Rama)LEVEL 01
Hebrew text of the 7 se'ifim with a fluent English translation. Gilui, the separation of meat and fish (kinuach ve-hadacha), human sweat, the dangerous practices, bal teshaktzu and the mesukenet animal explained with practical cases.
📖 StudyLEVEL 02
In-depth pilpul: gilui « לא נאסר במנין » (Taz sk1) contrasted with the chelev of siman 115, meat and fish cooked together forbidden even bediavad (סכנה ≥ איסור, צריך ששים אפילו ביבש במינו), the Rama's ספק סכנה, and the Taz / Maharshal debate on bal teshaktzu.
📖 StudyLEVEL 03
Comparative tables (lechatchila / bediavad, ריחא alone vs cooked together, gilui lifted vs the caution of the Gra), golden rules, classic pitfalls (kinuach ve-hadacha, ruach raa, bal teshaktzu) and memorization of the 7 se'ifim.
📖 StudyLEVEL 04
The practical halacha according to the Shach, Taz and Pitchei Teshuva, then the contemporary poskim on the principle סכנתא חמירא מאיסורא (Igrot Moshe, Tzitz Eliezer, Yabia Omer, Aruch HaShulchan): smoking, meat and fish, ruach raa. Note: the Shulchan Aruch HaRav does not deal with this siman — this is a level of psak, not "Daat HaRav".
📖 StudyThe Shulchan Aruch (YD 116:2-3) teaches that one does not eat meat and fish together because it is harmful to health (קשה לצרעת); the Rama adds not to roast them together (משום ריחא). In practice one separates them: between the two one performs kinuach ve-hadacha — that is, one eats and drinks something between the meat and the fish. This is one of the few דיני סכנה of the Shulchan Aruch still practiced every day. For practical halacha, consult your Rav.
This is the great principle of the Rama (se'if 5): the Torah commands one to preserve life and health, and one is stricter about danger than about an ordinary prohibition — one is more concerned about a doubt of danger than a doubt of prohibition. From here: שומר נפשו ירחק (whoever guards his soul keeps far away), the prohibition to rely on a miracle, and the duty to flee everything that leads to danger. Many contemporary poskim base on this their stance on smoking, reckless driving and health precautions. For practical halacha, consult your Rav.
The Sages forbade drinks left uncovered for fear that a snake had injected its venom into them (se'if 1). The Shulchan Aruch specifies that today, when snakes are not among us, it is permitted. It is a decree dependent on its reason: when the reason disappears the decree lapses (בטל הטעם בטלה הגזרה) — unlike the chalav of siman 115 which was « נמנה במנין ». The Taz (sk1) stresses this contrast, yet the Gra was nonetheless cautious. For practical halacha, consult your Rav.
Se'if 6 forbids eating or drinking what is repulsive — food mixed with vomit, excrement or fetid pus —, or in dirty vessels (chamber pots, bloodletting cups), or with soiled hands: all this falls under « אַל תְּשַׁקְּצוּ אֶת נַפְשֹׁתֵיכֶם » (do not make your souls repulsive). According to the Taz (sk6), one who transgresses receives makkat mardut and not malkut, since it is a לאו שבכללות. For practical halacha, consult your Rav.