The author continues until reaching the praises of Hakadosh Baruch Hu: "How much more so do we owe manifold and multiplied gratitude to the Omnipresent for all this: He brought us out of Egypt. He executed judgments upon them. He smote their gods. He slew their firstborn. He gave us their wealth. He split the sea for us. He led us through it on dry land. He drowned our enemies in it. He sustained us in the wilderness for forty years. He fed us the manna. He gave us Shabbat. He brought us before Har Sinai. He gave us the Torah. He brought us into Eretz Yisrael. He built for us the Beit Hamikdash to atone for all our sins."
Why is all of this based on fifteen? One must first understand that the entire Seder night is built upon the number fifteen. These are the fifteen elements of the Seder night: Kadesh, Urchatz, Karpas, Yachatz, Maggid, Rachtza, Motzi Matza, Maror, Koreich, Shulchan Oreich, Tzafun, Nareich, Hallel, Nirtza. What lies in the number fifteen, and why do we give thanks specifically fifteen times?
The Vilna Gaon writes in his Haggadah commentary: Fifteen levels are detailed here, corresponding to the name ה-י. They correspond to the levels from the earth to the heavens. The earth and the seven heavens make eight, and the seven spaces between them make fifteen. This is what is meant by: שׁ ִ י ר ו ּ לֵא-ל ֹהִ ים זַ מְּ רוּ שׁ ְ מ ו ֹ וּ סֹל לָרֹכֵב בּ ָ עֲ רָ ב וֹ ת בְּ יָ -הּ שׁ ְ מ ו ֹ וְ עִ לְ זוּ לְפָנָיו׃ Sing to G-d, sing praises to his name: extol him who rides upon the clouds; Y-ah is his name: and rejoice before him.
In response, David HaMelech composed fifteen Songs of Ascent (שׁ ִ י ר ל ַ מּ ַ ע ֲ ל ו ֹ ת) and there were fifteen steps in the Beit Hamikdash courtyard. When they would leave the courtyard, they would say: הּ וּלְ יָ - הּ עֵינֵינוּ -אָ נוּ לְ יָ. These also correspond to the fifteen generations from Avraham to Shlomo: Avraham, Yitzchak, Yaakov, Yehuda, Peretz, Chetzron, Ram, Aminadav, Nachshon, Salmon, Boaz, Oved, David, and Shlomo. The moon was full on the fifteenth of the month at the building of the Beit Hamikdash, where these fifteen elements conclude.
The commentators say that because we left Egypt on the fifteenth level, they established for us to recite fifteen praises after Shema: ָם, וְ יָשׁ ָ ר, וְ נֶאֱ מָ ן, וְ אָ הוּב, וְ חָ בִ יב, וְ נֶחְ מָ ד, וְ נָעִ ים, וְ יַצִּ יב, וְ נָכוֹן, וְ קַ יָּם, וְ נוֹרָא, וְאַדִּ יר, וּמְתוּקָן, וּמְקֻבָּל, וְטוֹב, וְיָפֶה . And it is established, and firm, and enduring, and upright, and faithful, and beloved, and cherished, and delightful, and pleasant, and awesome, and mighty, and correct, and accepted, and good, and beautiful.
