613 commandments

According to Jewish tradition, the Torah contains 613 commandments (Hebrew: תרי״ג מצוות, romanized: taryág mitsvót).
Although the number 613 is mentioned in the Talmud, its real significance increased in later medieval rabbinic literature, including many works listing or arranged by the mitzvot. The most famous of these was an enumeration of the 613 commandments by Maimonides. While the total number of commandments is 613, no individual can perform all of them. Many can only be observed at the Temple in Jerusalem, which no longer stands. According to one standard reckoning, there are 77 positive and 194 negative commandments that can be observed today, of which there are 26 commandments that apply only within the Land of Israel. In addition, some commandments only apply to certain categories of Jews: some are only observed by kohanim, and others only by men or by women.
Rav Hamnuna sourced the count of 613 in the verse Deuteronomy 33:4 ("Moses commanded us the Torah..."). The Talmud notes that the Hebrew numerical value (gematria) of the word Torah is 611 (ת‎ = 400, ו‎ = 6, ר‎ = 200, ה‎ = 5). Combining 611 commandments which Moses taught the people, with the first two of the Ten Commandments which were the only ones directly heard from God, a total of 613 is reached.
Other sources connect the tzitzit (ritual fringes of a garment) to the 613 commandments by gematria: the word tzitzit (Hebrew: ציצית, in its Mishnaic spelling) has the value 600 (צ‎ = 90, י‎ = 10, ת‎ = 400). Each tassel has eight threads (when doubled over) and five sets of knots. The sum of all these numbers is 613, reflecting the concept that tzitzit reminds its wearer of all Torah commandments.
Many Jewish philosophical and mystical works (e.g., by Baal HaTurim, the Maharal of Prague and leaders of Hasidic Judaism) find allusions and inspirational calculations relating to the number of commandments.
Rabbinic support for the number of commandments being 613 is not without dissent. For example, Ben Azzai held that there exist 300 positive mitzvot. Also, even as the number gained acceptance, difficulties arose in elucidating the list. Some rabbis declared that this count was not an authentic tradition, or that it was not logically possible to come up with a systematic count. No early work of Jewish law or Biblical commentary depended on the 613 system, and no early systems of Jewish principles of faith made acceptance of this Aggadah (non-legal Talmudic statement) normative. A number of classical authorities denied that it was normative:
Even when rabbis attempted to compile a list of the 613 commandments, they were faced with a number of difficulties:
Ultimately, though, the concept of 613 commandments has become accepted as normative amongst practicing Jews and today it is still common practice to refer to the total system of commandments within the Torah as the "613 commandments", even among those who do not literally accept this count as accurate.
However, the 613 mitzvot do not constitute a formal code of present-day halakha. Later codes of law such as the Shulkhan Arukh and the Kitzur Shulkhan Arukh do not refer to it. However, Maimonides' Mishneh Torah is prefaced by a count of the 613 mitzvot.
There is no single definitive list that explicates the 613 commandments. Lists differ, for example, in how they interpret passages in the Torah that may be read as dealing with several cases under a single law or several separate laws (see here for a visual comparison of several lists). Other "commandments" in the Torah are restricted as one-time acts, and would not be considered as "mitzvot" binding on other persons. In rabbinic literature, Rishonim and later scholars composed to articulate and justify their enumeration of the commandments:
The following are the 613 commandments and the source of their derivation from the Hebrew Bible as enumerated by Maimonides: