?Minchasah u?Nesachehah?. Why does the Torah change here to the plural?
Rashi: Refer to 29:19:1:1.
Targum Yonasan and Ta?anis, 2b (citing R. Akiva): To teach us that both the Nisuch ha'Yayin and the Nisuch ha'Mayim apply (only) on that day. 1
Torah Temimah: And we nevertheless need the D'rashah of 'Mayim' - Refer to 29:19:1:1 - to teach us that one of the Nisuchim is with water, and not both with wine. See Ta?anis 2b & 3a.