Hallel on the Seder Night

The Rambam in Hilchos Chanuka (3:6) says:

ולא הלל חנוכה בלבד, הוא שמדברי סופרים, אלא קריאת ההלל לעולם מדברי סופרים, בכל הימים שגומרין בהן את ההלל

Not only is hallel on Chanuka miderabonon but reading hallel is always miderabonon on all days when we complete hallel.

The ra’avad asks:

 אמר אברהם ויש בהם עשה מדברי קבלה השיר יהיה לכם

How can the Rambam say that hallel is always derabonon? Sometimes the chiyuv to say hallel is more than a miderabanan, it is from the neviim, as it says in Yeshaya (30:29): הַשִּׁיר יִהְיֶה לָכֶם, כְּלֵיל הִתְקַדֶּשׁ-חָג

The possuk is talking about the downfall of Sancheriv, and says that when Sancheriv is destroyed, the benei Yisroel will say shiroh as on the first night of Pesach. You see from here that the chiyuv to say hallel on the seder night is midivrei neviim, not simply miderabonon?

The Brisker Rov (Hilchos Chanuka, 3:6) answers as follows:

The Ran at the end of the second perek of Megilla asks why we do not say a beracha when we say hallel on the seder night. The Ran quotes Rav Hai Gaon who says:

שאין אנו קורין אותו בתורת קורין, אלא בתורת אומר שירה

"We do not read the hallel on the seder night as a recital, but rather as a way of saying shiroh."

What does Rav Hai Gaon mean?

What is the difference between the way that you say hallel on the seder night and the way that you say hallel the whole year round?

Rav Betzalel Zolty z”l in Mishnas Yaavetz explains as follows:
In the Haggada we say:

בְּכָל דּוֹר וָדוֹר חַיָּב אָדָם לִרְאוֹת אֶת עַצְמוֹ כְּאִלוּ הוּא יָצָא מִמִּצְרַיִם ... לֹא אֶת אֲבוֹתֵינוּ בִּלְבָד גָּאַל הַקָּדוֹשׁ בָּרוּךְ הוּא, אֶלָּא אַף אוֹתָנוּ גָּאַל עִמָּהֶם ...לְפִיכָךְ אֲנַחְנוּ חַיָּבִים לְהוֹדוֹת, לְהַלֵל...

"In every generation a person is obligated to see as if they themselves came out of mitzraim, not only did Hashem redeem our forefathers but He also redeemed us with them, therefore we are obligated to thank, to praise.."

On the seder night, we see ourselves as if we are being redeemed now, therefore we say shiroh. On all other days of the year, we say hallel either because we are happy, for example on Yom Tov, or because we celebrate a past yeshua, as on Chanuka. Only on the seder night do we say hallel because we consider ourselves to have been redeemed now from slavery. That is why we do not make a beracha. A beracha is an expression of gratitude to Hashem and shiroh is also an expression of our gratitude to Hashem. It would not make sense to say a beracha on shiroh becuase this beracha would mean – thank you Hashem for telling us to say thank you. By the same token one could say a beracha on a beracha.

With this Rav Hai Gaon, the Brisker Rov answers the question of the Raavad on the Rambam.

The Rambam is talking about hallel said the rest of the year, as the Rambam continues:

...קריאת ההלל לעולם מדברי סופרים, בכל הימים שגומרין בהן את ההלל. ושמונה עשר יום בשנה, מצוה לגמור בהן את ההלל; ואלו הן--שמונת ימי החג, ושמונת ימי חנוכה, וראשון של פסח, ויום עצרת.

"Saying hallel is always miderabanan on all the days that hallel is completed. There are 18 days in the year when it is a mitzva to finish hallel, which are; The 8 days of succos, 8 days of chanuka, the first day of Pesach and the first day of Shevuos."

The Rambam does not mention hallel on the seder night because this is a different type of hallel altogether. It is not a chiyuv to read the hallel, rather it is a natural expression of thanks to Hashem for the geulah that we experience on the seder night

The Rambam agrees with the Ra'avad that hallel on the seder night is midivrei neviim and not only miderabanan. Nevertheless he is still justified in saying that the din of being gomer hallel is always miderabanan, becuase hallel on the seder night is not in the same category as hallel the rest of the year.