Why was Moshe's prayer that the Arov would disappear "tomorrow" -- rather than today?
Ramban: Once again, Moshe took his cue from Pharaoh, who said "tomorrow" by the plague of frogs (8:6). 1
Rosh (to 8:14): Some of the beasts move slowly, so it required a day to leave Mitzrayim.
Maharal (Gevuros Hashem Ch. 33, p. 125): That day had already been stricken by the Makah. The Arov would not disappear on that same day. 2
Refer also to 9:5:1.
Gur Aryeh (to 8:5) writes the same regarding Makas Tzefarde'a; refer to 8:6:1:6. Gur Aryeh (ibid.) contrasts this with Barad; the hail would in fact stop mid-day, because each hailstone is a new strike (and thus the day as a whole had not been "stricken"). However, Gur Aryeh (ibid.) classifies Arov along with Barad; as packs of wild animals will come and go, and therefore the plague could disappear immediately! This seems to contradict both what Maharal writes in Gevuros Hashem, and indeed the Pasuk itself - Moshe tells Pharaoh that the plague would disappear only tomorrow! Perhaps we can answer, that Gur Aryeh is telling us Pharaoh's perspective. Pharaoh understood why the plague of frogs could end only the next day; yet regarding Arov, he presumably requested (8:24) that the wild beasts be removed immediately (reasoning that they are transient). In Gevuros Hashem, Maharal explains Moshe's response - that no, the Arov would also have to wait until tomorrow to disappear. (EK)
Rashi (to 8:27) comments that the Arov "was removed;" i.e. the animals simply vanished (rather than dropping dead, as the frogs had done). Why doesn't Rashi derive this from our verse, "v'Sar he'Arov"?
Refer to 8:27:1.1:1.
Rashi (to 7:25) wrote that each plague lasted one full week, a quarter of a month. In the Makah of Arov (and other Makos as well), Moshe prayed that the Makah should end. If seven days had already elapsed, why did Moshe have to pray? If seven days had not yet passed, then the Makah was not in force for its full duration!
Gur Aryeh (to 8:5): Even when a Makah was cut short by Moshe's Tefilah, Pharaoh lived in fear that it would return at any moment. (In that sense, these Makos also lasted the full week.)
Maharal #1 (Gevuros Hashem, beg. Ch. 33, p. 124): The Makah itself lasted seven days, yet its after-effects would have lingered far beyond, had Moshe not prayed. Moshe's prayer caused that the Arov that was already present would disappear.
Maharal #2 (ibid.): Each plague was to last for seven days - provided that Pharaoh did not agree to free the Bnei Yisrael. When Pharaoh said that he would free them, this completed the Makah. Moshe's prayer was then effective in removing its effects - even during the seven days. 1
