Blessings on Rabbinical Mitzvahs
On Chanukah and Purim, we say the blessing, Asher Kidishanu - "Which God has commanded us..." Yet aren't those words inappropriate, given that nowhere in the 613 mitzvahs of the Torah are these holidays mentioned.
The Aish Rabbi Replies:
There are two types of mitzvahs: Torah-level and Rabbinic-level.
Torah-level refer to the 613 mitzvahs delineated in the Five Books of Moses.
Rabbinic mitzvahs are legislated by the Sages. The reason we say the same blessing ("which God has commanded us") is because the Torah itself gave the power of legislation to the Sages. Deuteronomy 17:8-13 describes what to do when faced with difficult questions of Jewish law. We are told to travel to the judges in Jerusalem and follow their decision. Verse 11 states, “You may not veer from the word they tell you right or left.” The rulings of the Sanhedrin (high court) are binding and the laws of the Torah follow its decisions.
The Talmud (Shabbat 23a) likewise asks why do we bless “Blessed are You, God… who commanded us to light the candle of Hanukkah” – if it was the rabbis who obligated us. It suggests two different verses. The first is Deut. 17:11 as we quoted above. The second is Deut. 32:7: “Ask your father and he will tell you, your elders and they will say to you” – which likewise teaches us to follow the instructions of our wise men.
There is much discussion in the early authorities as to the extent and ramifications of the commandment known as “you may not veer.” According to some, it grants rabbinical decrees precisely the same authority as Torah law while others see it as more of an allusion. It is likewise discussed which types of rabbinical decrees the verse applies to. Regardless, the general notion clearly exists that the Sages may make further decrees upon Israel and the nation is bound to follow them.
In fact, Rabbi Moshe Chaim Luzzatto wrote: "God's authority decreed that these Rabbinic mitzvahs be kept just like the Torah mitzvahs... One who violates these transgresses God's word as much as one who violates the explicit commandments."
There are seven Rabbinic mitzvahs for which we make a blessing. They are:
1) washing of the hands before bread
2) lighting of Sabbath Candles
3) lighting of the Festival candles
4) making an Eruv (carrying area for Shabbat)
5) reciting Hallel (Psalms of praise as said on certain holidays)
6) lighting the Chanukah menorah
7) reading the Megillah on Purim
(Sources: Talmud Brachot 19b, Shabbat 23a with Ritva, Rambam Sefer HaMiztvot Shorashim 1 with Ramban, Rambam Mamrim 1:1-2.)