And their meal-offerings and their libations, for the bulls: The seventy bulls of the [’Succoth’] festival corresponded to the seventy nations, which progressively decrease in number, symbolizing their [the nations’] destruction [Midrash Aggadah]. At the time of the Temple, they [the sacrifices] shielded them from adversity [Mid. Tehillim 109:4, Rashi on Sukkah 55b; Rashi on Ps. 109:5; Mid. Tadshei ch. 11; Pesikta d’Rav Kahana pp. 193b, 194a; Mid. Song Rabbah 4:2, Mid. Tanchuma Pinchas 16].
and for the lambs: corresponding to Israel, who are called ‘a scattered lamb’ (Jer. 50:17). Their number remains constant, and it totals ninety-eight, to counter the ninety-eight curses related in ‘Mishneh Torah’ [the Book of Deuteronomy] (28:15-68) (Mid. Aggadah). On the second day it says, וְנִסְכֵּיהֶם, “and their libations” relating to the two daily continual offerings. The language [of Scripture] varies only for expository purposes, following our Sages, of blessed memory, who said: On the second day, וְנִסְכֵּיהֶם, “and their libations”; on the sixth day, וּנְסָכֶיהָ “and its libations”; on the seventh day כְּמִשְׁפָּטָם “as prescribed for them” [instead of כַּמִּשְׁפָּט,“as prescribed”]. [The additional letters in these three words are] ‘mem’ ’yud’ ‘mem’ which form [the word] מַיִם, ‘water.’ This suggests that the [ceremony of] water libation during the festival [of 'Succoth’] is of Torah origin. — [Sifrei Pinchas 54, Ta’anith 2b]
