Rabbinic Mitzvos #1 - Hallel

In both a positive mitzvah (#495) and a negative mitzvah (#496), the Torah requires us to follow rabbinic enactments. Seven of these are considered the “Sheva Mitzvos d’Rabbanan,” the “Seven Rabbinic Mitzvos.” It would appear that the basis for categorizing these enactments as “rabbinic mitzvos” is that –with one obvious exception–these are the ones on which the Rabbis instituted that brachos should be recited “that God sanctified us with His commandments and commanded us to…” The Talmud, when discussing these enactments, typically asks, “Where did God command us to do that?” It then answers by referring us to the Torah’s requirement to follow rabbinic laws.

The Sages instituted to recite the Psalms of praise that we call Hallel on the following occasions: the eight days of Succos, the eight days of Chanukah, the first day of Pesach and the one day of Shavuos. Outside of Israel, where an extra day of Yom Tov is observed, Hallel is also recited on Simchas Torah, the second day of Pesach and the second day of Shavuos.

Hallel on Rosh Chodesh is just a minhag, which is why we recite the abbreviated version commonly referred to as “half-Hallel.” Similarly, Hallel was only instituted for days of Yom Tov that have their own unique musaf sacrifices, such as the eight days of Succos. Since the musaf sacrifice is the same on each day of Passover, Hallel was only instituted on the first day. The custom is therefore to recite “half-Hallel” for the rest of the Passover.

Hallel is discussed in the Talmud in tractate Arachin on pages 10a-b and in Taanis on page 28b. It is codified in the Shulchan Aruch in Orach Chaim 422.