1)
Why does the Torah change here to the plural ? "u'Nesachehah"?
1.
Rashi: Refer to 29:19:1:1.
2.
Targum Yonasan: The Torah writes "u'Nesachehah" (in the plural, on the sixth day, to teach us that both the Nisuch ha'Yayin and the Nisuch ha'Mayim apply on that day. 1
3.
Ta'anis, 2b (citing R.Akiva): To teach us that there are two Nisuchim. one of wine and one of water. 2