On clear food and unclean food

The Torah's dietary laws — kashrut (כַּשְׁרוּת, the system of permitted and forbidden foods) — form one of the most distinctive pillars of Jewish observance. The Torah provides clear criteria distinguishing tahor (טָהוֹר, ritually pure/permitted) from tamei (טָמֵא, ritually impure/forbidden) foods, rooted in the call to holiness.

Key Takeaways

Land animals must have split hooves and chew their cud to be permitted — failing either one makes the animal forbidden.
Fish must have fins and scales to be permitted; shellfish and seafood without both are forbidden.
Birds: The Torah lists forbidden species by name; traditionally, only birds with an established mesorah (tradition) of being eaten are permitted.
Insects and crawling creatures are universally forbidden.
The laws of kashrut are grounded in the Torah's call to kedushah (קְדֻשָּׁה, holiness) — "Be holy, for I am holy."

The Biblical Foundation

Land Animals

The primary source is Leviticus 11:1–8 and its parallel in Deuteronomy 14:3–8. The Torah states:

"זֹאת הַחַיָּה אֲשֶׁר תֹּאכְלוּ מִכׇּל־הַבְּהֵמָה אֲשֶׁר עַל־הָאָרֶץ — This is the animal that you may eat from among all the land animals..." [Leviticus 11:2]

The two required signs (simanim, סִימָנִים) are:

מַפְרֶסֶת פַּרְסָה — split hooves
מַעֲלַת גֵּרָה — chewing the cud (rumination)

An animal must have both signs. The Torah then explicitly names four animals that have only one sign and are therefore forbidden [Leviticus 11:4–7]:

| Animal | Has | Lacks | |--------|-----|-------| | Camel (גָּמָל) | Chews cud | Split hoof | | Hyrax (שָׁפָן) | Chews cud | Split hoof | | Hare (אַרְנֶבֶת) | Chews cud | Split hoof | | Pig (חֲזִיר) | Split hoof | Chews cud |

The pig is considered especially problematic in Jewish tradition because it displays its split hoof (as if to say "I am kosher") while hiding its lack of cud-chewing — symbolizing hypocrisy [Midrash Vayikra Rabbah 13:5].

Examples of permitted animals include: ox, sheep, goat, deer, and gazelle [Deuteronomy 14:4–5].

Fish and Sea Creatures

The Torah permits fish that have both:

סְנַפִּיר (snapir) — fins
קַשְׂקֶשֶׂת (kaskeśet) — scales

All shellfish (shrimp, lobster, crab, oysters) and creatures lacking both signs are forbidden [Leviticus 11:9–12].

Birds

Rather than giving signs, the Torah lists 24 forbidden bird species [Leviticus 11:13–19; Deuteronomy 14:12–18]. The Talmud does provide general signs for forbidden birds [Chullin 59a], but because identification of species is uncertain, the accepted practice is:

Only birds with an established mesorah (מָסוֹרָה, unbroken tradition) of being eaten in a community are permitted.

Common permitted birds: chicken, turkey, duck, goose. Raptors and birds of prey are all forbidden.

Insects and Creeping Things

The Torah is emphatic:

"אַל־תְּשַׁקְּצוּ אֶת־נַפְשֹׁתֵיכֶם בְּכׇל־הַשֶּׁרֶץ הַשֹּׁרֵץ — Do not make yourselves detestable through any swarming creature that swarms..." [Leviticus 11:43]

And in Leviticus 20:25:

"וְלֹא־תְשַׁקְּצוּ אֶת־נַפְשֹׁתֵיכֶם בַּבְּהֵמָה וּבָעוֹף — You shall not make yourselves detestable through beast or bird..."

The prohibition on insects is one of the strictest in kashrut — eating even a single insect can involve multiple Torah violations. This is why checking vegetables like lettuce, broccoli, and herbs for insects (bedikat tola'im, בְּדִיקַת תּוֹלָעִים) is a serious halachic concern.

The exception: certain species of locusts (arbeh, אַרְבֶּה) are permitted by Torah law [Leviticus 11:22], though only communities with a clear tradition (like Yemenite Jews) still eat them.

The Spiritual Dimension — Why These Laws?

The Torah ties kashrut directly to holiness:

"כִּי אֲנִי יְהֹוָה אֱלֹהֵיכֶם וְהִתְקַדִּשְׁתֶּם וִהְיִיתֶם קְדֹשִׁים כִּי קָדוֹשׁ אָנִי — For I am the LORD your God: sanctify yourselves and be holy, for I am holy." [Leviticus 11:44]

Several major thinkers offer different rationales:

Rambam (Maimonides, Mishneh Torah and Guide for the Perplexed 3:48): Forbidden foods are physically harmful to the body and damage health.
Ramban (Nachmanides, Commentary to Leviticus 11): Forbidden foods have a spiritual effect — they coarsen the soul and dull spiritual sensitivity.
Sefer HaChinuch (Mitzvah 73): The laws train us in self-discipline (shmirat hanefesh, שְׁמִירַת הַנֶּפֶשׁ) — mastering our physical appetites.
Rabbi Samson Raphael Hirsch: Kashrut teaches that we do not live to eat; the Jew subordinates physical consumption to divine will.

Additional Rabbinic Laws

Beyond the Torah's categories, the Rabbis added:

Basar b'chalav (בָּשָׂר בְּחָלָב) — prohibition of mixing meat and dairy [Exodus 23:19, as interpreted by the Talmud, Chullin 115b]
Shechita (שְׁחִיטָה) — ritual slaughter requirements for meat
Bishul Akum — food cooked by non-Jews in certain circumstances
Yayin Nesech — restrictions on non-Jewish wine

For personal guidance on kashrut observance or specific questions, consult your local rabbi or posek.