It is customary to read the Book of Rut on Shavu’ot. According to the Midrash, this is “to teach you that the Torah is acquired only through poverty and suffering…. The Torah asked of God: ‘Master of the universe, throw my lot in with the poor, for if the wealthy study me, they will become arrogant, while poor people who study me are aware that they are lowly and hungry’” (Yalkut Shimoni, Rut, §596). In this megilla we see the fulfillment of the mishnaic proclamation: “Anyone who keeps the Torah while poor will eventually keep it while rich, while anyone who ignores the Torah while rich will ultimately ignore it while poor” (Pirkei Avot 4:9). Ruth lived long enough to see her descendants David and Shlomo sitting on the throne.
A second reason for reading this megilla on Shavu’ot is that Israel’s acceptance of the Torah at Sinai was in effect their conversion to Judaism. Rut’s conversion, as portrayed in the megilla, can be seen as a continuation of that event (Abudraham). A third reason is that it was on Shavu’ot that King David died. The Book of Rut deals with his lineage, as we read at its end: “And Yishai begot David” (Birkei Yosef 494:11). A fourth reason is that “This scroll contains neither laws about purity and impurity, nor laws about what is permitted and prohibited. Why then was it written? To teach how great the reward is for performing acts of kindness” (Rut Rabba 2:14). Encouraging kindness is the primary purpose of Torah, as we read: “The Torah begins with an act of kindness and ends with an act of kindness” (Sota 14a). This is also expressed by R. Akiva’s declaration: “‘Love your fellow as yourself’ is a vital principle of the Torah” (Sifra, Kedoshim).
As we saw above (2:10), some Ashkenazim read from a megilla written on parchment, reciting the berakhot of “al mikra megilla” and She-heḥeyanu beforehand. This is the custom of the Vilna Gaon’s followers. The custom of most Ashkenazim and all Sephardim is not to recite a berakha before reading. They also do not insist on reading from parchment.
In Ashkenazic countries, the custom was to read the megilla at Shaḥarit before the Torah reading on Yom Tov Sheni. However, if necessary it may be read at another time. Therefore, in Eretz Yisrael, some of those who stay up all night read the megilla before Shaḥarit, or after Minḥa so they will be able to concentrate on it better.
Sephardim and Yemenites generally read Megillat Rut before Minḥa. If they have already read it during their Shavu’ot night learning, it is not necessary to read it again before Minḥa.