Despite the rabbinic concept that there are 613 biblical commands, a careful examination produces a much smaller number. Interestingly, in his list of the 613 Maimonides included commands that the rabbis said were biblical in origin, even though they are not explicit in the Torah. The following is from my recent book “Mysteries of Judaism II: How the Rabbis and Others Changed Judaism.”
Rabbi Simlai’s Sermon
The first report that the Torah contains 613 commandments dates to the third century CE, when Rabbi Simlai mentioned this concept in a sermon that is recorded in the Babylonian Talmud, Makkot 23b. The Talmud states: “Rabbi Simlai gave as a sermon [darash Rabi Simlai]: 613 commandments were communicated to Moses – 365 negative commands, corresponding to the number of solar days [in a year], and 248 positive commands, corresponding to the number of the members [bones covered with flesh] of a man’s body.” It thus appears that Rabbi Simlai invented the number 613 because it fit his sermon: A person should observe the Torah with all his body parts (248) every day (365). The two numbers add up to 613.
As far as we know, no one thought there were 613 biblical commandments before Rabbi Simlai offered his sermon. In fact, 150 years before Rabbi Simlai, ben Azzai is quoted as saying that there were three hundred biblical commands. E. E. Urbach wrote: “In the Tannaitic sources this number  is unknown.”
The Reactions of Abraham ibn Ezra, Nachmanides, and Others
Ibn Ezra (1089–1167) recognized that if one counts all of the divine commandments recorded in the Bible, the number would be well over a thousand; and that if only the commandments relevant to his day were numbered, the total would be less than three hundred. He wrote in his Yesod Moreh 2: “Some sages enumerate 613 mitzvot [divine commandments] in diverse ways…but the truth is that there is no end of the number of mitzvot…and if we were to count only the root principles…the number of mitzvot would not reach 613.”
Nachmanides (1194–1270) writes in his Hasagot, his critical commentary to Maimonides’s Sefer Hamitzvot, that the 613 count is a matter of dispute and there is no certainty that it is true, but since “this total has proliferated throughout the aggadic literature…we ought to say that it is a tradition from Moses at Sinai.”
Judah ibn Balaam (eleventh century) rejected the notion that there are 613 biblical commands. He wrote “To my mind, the dictum [of Rabbi Simlai] was said only as an approximation.”
Gersonides (1288–1344) also rejected the idea that there are 613 biblical commandments. He wrote that the number is only homiletical, teaching that Jews should obey God’s laws with their entire being (248 organs) every day (about 365 days in the solar calendar).
Rabbi Shimon ben Tzemach Duran (1361–1444) summed up the above-mentioned views: “Perhaps there is agreement that the number 613…is just Rabbi Simlai’s opinion, following his own explication [account] of the mitzvot. And we need not rely on his explication when we come to determine the law, but rather on the Talmudic discussion.”
It should come as no surprise, therefore, that early attempts to list the 613 commandments failed. In his introduction to his own listing in Sefer Hamitzvot, Maimonides pointed out some attempts to list the 613, including such errors as inserting post-biblical rabbinic commandments such as the lighting of Chanukah candles into the list of biblical commandments.
Maimonides’s itemization of the 613 biblical commandments is the most logical, but it is not accepted by all rabbis. Nachmanides, for example, rejected some of Maimonides’s items and included others.
There is one serious problem with Maimonides’s list of biblical commands. Most of the laws in Maimonides’s list, if not all of them, have been modified and explained by the rabbis in ways that are not explicit in the Torah. For example, Rashbam (c. 1085–c. 1158) recognized that when the Bible states that a particular law shall be “a sign between the eyes and a sign on the hand” it means that the law should be remembered always, whenever you look at or do anything. Rashbam was explaining that the law of tefillin, which the rabbis derive from these verses, is not the original biblical intent. Yet Maimonides includes tefillin as two of the 613 biblical commandments – listing a commandment that was apparently enacted by the rabbis and, in any event, not explicitly written in the Torah.
How should Maimonides be interpreted? It would be absurd to say that Maimonides did not realize that virtually all, if not all, of the commandments that he enumerated are rabbinic interpretations of the Bible, not explicit biblical commandments. Thus, although he does not say so, we should understand that he listed those commandments that the rabbis said were biblical in origin, even though they are not explicit in the Torah. The rabbis classified them as biblical because they used biblical words as pegs (asmakhtot) for their laws.
In short, a careful examination of Maimonides’s Sefer Hamitzvot, which contains his listing of the 613 commands, and his Mishneh Torah, his code of Jewish laws, shows that the rabbis changed Judaism. They gave the Hebrew Bible a meaning that is not the literal meaning of the text, changed the biblical laws, and invented laws that were later included in the list of 613 biblical commands.
How Many of the Commands Are Relevant Today?
Not only is the number 613 the result of a third-century sermon, with the list debated by many rabbis and including commands instituted by the rabbis who considered them “as if” they were biblical, but most of the inventory of 613 commands are not relevant today.
In his Sefer Hamitzvot, Maimonides enumerated the positive commandments that “a Jew in the ordinary course of life has always the opportunity to fulfil.” Maimonides records only 60 positive commands, not 248, that are applicable to men. The number for women is only 46. Chavel states that one could add 23 other commands to the list, commands that were added by Rabbi Israel M. Kagan (the Chafetz Chaim, 1839–1933). These are laws that most Jews rarely if ever need to observe, such as redeeming the firstling of an ass, canceling claims in the Sabbatical year, and unloading a tired animal. Even if these 23 are added to Maimonides’s 60 for men and 46 for women, the total of 83 and 69 fall far short of 248, the traditional number of positive commandments.
 Sifrei Deuteronomy 76.
 The Sages: Their Concepts and Beliefs (Cambridge, MA: Harvard University Press, 1987).
 By “diverse ways,” ibn Ezra meant that rabbis differed in what they included in the 613 “biblical commandments.” The most famous catalogue is that of Maimonides, discussed below, who included beliefs in his list. In contrast, Bachya ibn Pakuda (eleventh century) considered that only practical duties and not beliefs should be included, so he had a different list of 613 commands. Ibn Pakuda’s list appears in Sefer Torat Chovot Halevavot (Jerusalem: Feldheim, 1984).
 See the Ramban’s introduction to his Hasagot, especially page 6, in Sefer Hamitzvot l’Harambam im Hasagot Haramban, ed. Charles Ber Chavel (Jerusalem: Mossad HaRav Kook, 1981). Nachmanides’s willingness to call a doubtful idea “a tradition from Moses at Sinai” is remarkable. It is clear that what he means by the term is not that these laws were literally obtained by Moses from God at Sinai, as many think, but since the notion of 613 commandments has become part of Jewish tradition, we should consider the idea as important as if it had been revealed at Sinai.
 Harkavy, Abraham E., “Zikhron Hagaon Rav Shmuel ben Hofni u’Sefarav,” in Zikaron la’Rishonim v’Gam la’Acharonim (St. Petersburg, 1880), 1:41–42. Also cited by Yerucham Perla in his introduction to Sefer Hamitzvot – Rasag (Jerusalem, 1973).
 See Menachem Kellner, Torah in the Observatory: Gersonides, Maimonides, Song of Songs (Boston: Academic Studies Press, 2010).
 In Zohar Harakia (Academic Studies Press, 2012).
 For example, Maimonides did not include a command to dwell in Israel in his list, whereas Nachmanides did.
 Exodus 13:9, 16; Deuteronomy 6:8–9 and 11:18.
 The rabbis use two terms to classify the origin of laws: mi’d’oraita, “from the Torah,” and mi’d’rabbanan, “from the rabbis.” These terms should not be taken literally. A law is often considered to be mi’d’oraita even though it is clearly not mentioned in the Torah, because the rabbis found an asmakhta, a pin or nail upon which they could hang their decree.
Albert D. Friedberg also noted that Maimonides included rabbinic laws in his itemization of 613 commandments. See Crafting the 613 Commandments: Maimonides on the Enumeration, Classification, and Formulation of the Scriptural Commandments (Academic Studies Press, 2014). Friedberg writes: “[Amid] the heavily politicized atmosphere of Cairo, where Rabbinites were both assiduously courted and continuously attacked by sectarian groups [largely Karaites] over the role of the oral law in interpreting Scripture, Maimonides chose to keep his radical opinions hidden yet recoverable. When applied to the legal sections of the Torah, Maimonides’ peshateh di-qera hermeneutics [interpreting Scripture according to its plain meaning in context rather than the manner that rabbis used to teach their laws] would likely raise hackles among his own co-religionists and, worse yet, give comfort to the deniers of the oral law. His carefully planted literary clues could lead the reader who is familiar with rabbinic terminology and unburdened by popular and superficial conclusions to discover the Master’s true opinion or at the very least sense his ambivalence.”
 One way of seeing this is to note what Maimonides states is a biblical command and then look at the verse that he cites to show where the Torah mentions the command. In many instances, this examination will reveal that the quoted text does not explicitly mandate the command. A further examination will reveal that even if the Bible text does contain the command, the details of its implementation are not in the Torah, but were developed by the rabbis. Examples of commands in Maimonides’s list that are not really in the Bible include a mandate to believe in God, cleaving to God, reading Shema, studying the Torah, the two commands regarding tefillin, mezuzot, Grace after Meals, shechita, counting the omer, fasting on Yom Kippur, resting on Yom Kippur, reading the prophets, and abiding by a majority decision.
 Maimonides: The Commandments, trans. Charles B. Chavel (Soncino Press, 1967), 348–49.
 In Sefer Ha-Mitzvoth Hakotzer, published by Rabbi David Katz, 2000.
 Maimonides did not itemize the negative commands that are relevant today, probably because strictly speaking, all of the prohibitions are in effect today, even though in many instances people do not have an opportunity to transgress the prohibitions. Rabbi Israel M. Kagan listed 200 negative commands, again far short of the traditional number 365. The total, according to Rabbi Kagan’s register, is 283, less than half of 613.