Rabbi Simlai taught: There were 613 mitzvot stated to Moses in the Torah.
Yet, as Marc Herman points out, “there is perhaps no idea that is simultaneously as widely accepted, yet with so little basis in rabbinic literature, as the supposition that it is ‘unambiguous’ that Jewish law consists of precisely 613 commandments.” The Torah never enumerates its commandments. And while the Talmud preserves Rabbi Simlai’s teaching, it never presents a list.
It does, however, regularly distinguish between biblical commandments (d’oraita, or from the Torah) and obligations that are derived from the rabbis (d’rabbanan, or from the rabbis). And just as there is some messiness about what makes the list of biblical mitzvot, there is some lack of clarity about the line that separates biblical obligations from rabbinic ones as well.
On today’s daf, we find a mishnah which teaches a general principle that summarizes what we have already learned:
Whoever is forbidden by a prohibition of forbidden relations to her yavam neither performs halitzah nor enters into levirate marriage.
This rule is followed by another:
If she is forbidden by a prohibition resulting from a mitzvah … she performs halitza.
But wait, what’s the difference between a prohibition of forbidden relations and a prohibition resulting from a mitzvah? Aren’t they the same thing? They can’t be because in the former case yibbum and halitzah are forbidden, while in the latter halitzah is required.
Sensing the potential for confusion, the mishnah explains:
A prohibition resulting from a mitzvah is referring to secondary forbidden relationships, which are prohibited by rabbinic law.
In other words, there are relationships forbidden by the Torah and there are secondary forbidden relationships that were proscribed by the rabbis. There is one rule for the former category, another for the latter.
But wait a minute, if the second phrase refers to rabbinic prohibitions, why would it use the word mitzvah, which connotes a biblical precept? As it happens, the Gemara asks this as well, and Abaye responds:
This is because it is a mitzvah to listen to and obey the words of the sages.
Abaye, in fact, has a leg to stand on. The Torah (Deuteronomy 17:8-11) invests authority in the leaders of the community. So by listening to them, we are in fact also listening to the Torah.
Abaye’s teaching expands the notion of mitzvah to include rabbinic rules. If it’s a mitzvah to listen to the rabbis, then by following what they teach we are, in fact, following a biblical commandment even when the particulars are rabbinic in origin. This is why the lighting of Shabbat candles and the Hanukkah menorah — neither of which are mentioned in the Torah — are preceded by a blessing honoring God who “sanctified us with God’s commandments.” This phrase is normally reserved for practices with biblical origins, but it’s used in these cases to refer to those established by the rabbis.
Strict constructionists would have us limit the use of the word “mitzvah” to biblical commandments. But in the modern era, the distinctions between biblical and rabbinic obligations have become far less relevant to both our day-to-day practice and our notion of what constitutes a mitzvah. Many consider all Jewish actions to be mitzvot, including those that support our sense that Judaism wants us to be good and ethical people.
So while 613 might be the traditional answer to how many mitzvot are in the Torah, in practice Jews have never really restricted their Jewish obligations, biblical or otherwise, to this or any other number. The rabbinic endeavor is expansive, as are the ways Jews have sought to live a life of Torah. And while it might be convenient to have an agreed-upon number of biblical mitzvot, there are an infinite number of pathways through which we might put them into practice.
Read all of Yevamot 20 on Sefaria.