וְחַגֹּתֶ֤ם אֹתוֹ֙ חַ֣ג לַֽיהוָ֔ה שִׁבְעַ֥ת יָמִ֖ים בַּשָּׁנָ֑ה חֻקַּ֤ת עוֹלָם֙ לְדֹרֹ֣תֵיכֶ֔ם בַּחֹ֥דֶשׁ הַשְּׁבִיעִ֖י תָּחֹ֥גּוּ אֹתֽוֹ׃
每年七日，你們要守這節，作為向永恆者守的節。這是你們世世代代永遠的定例；你們要在七月守這節。
Mekhilta DeRabbi Yishmael
R. Yossi Haglili says: It is written (Devarim 16:15) "Seven days shall you celebrate ('tachog') to the L–rd your G–d," to include the seven days of Pesach as requiring a chagigah. But perhaps it speaks only of Succoth? (This is not so, for Leviticus 23:41) "And you shall celebrate it as a festival of the L–rd" already speaks of Succoth. How, then, are we to understand "Seven days shall you celebrate"? To include the seven days of Pesach as requiring a chagigah.
Sifrei Devarim
If so, how is "seven days" to be understood? As referring to compensation (i.e., if he did not offer the chagigah on the first day, he can do so all seven days.