After the first three plagues, Hashem resumes His practice of warning Pharaoh before bringing the fourth plague:

And Hashem said to Moshe, “Arise early in the morning and present yourself before Pharaoh – behold, he goes out to the water – and you shall say to him: ‘Thus says Hashem, Release My people so that they will serve Me. For, if you do not release My people, behold I provoke (MASHLIACH) against you, and your servants, and your people, and your household the AROV; and the houses of Egypt shall be full of ‘AROV, as well as the ground on which they are. And I shall set apart, on that day, the land of Goshen where My people remain, for the AROV not to be there, so that you will know that I Hashem am in the midst of the land. And I shall place salvation between My people and your people. Tomorrow shall this sign be.’”

And Hashem did so, and severe AROV came to Pharaoh’s house and his servants’ house, and throughout the land of Egypt the land was destroyed because of the AROV (Shemot 8:16-20).

From the context it is clear that AROV is very dangerous: it fills the houses and even destroys the land. However, there is little evidence from the text to identify ‘AROV. Most Midrashim and commentaries agree that AROV is a “mixture” of deadly creatures, such as lions, bears, tigers, wolves and predatory birds, along with snakes, scorpions and insects. [That would mean that the lice of the third plague are invited back!] This position is based on the views of R. Akiva and R. Yehudah, that the AROV came “from above and from below” (Shemot Rabbah 11:3, 4).

Ibn-Ezra quotes the verse in Tehillim:
He released (YESHALACH) AROV against them which consumed them (78:45).

Not only does this verse use a similar verb to the one in our passage (YESHALACH—MASHLIACH), but it also supports the contention that AROV is a mixture of devouring creatures, although Ibn-Ezra admits that it may refer to one such species. Rashbam sees the connection between AROV and EREV (“evening”), and therefore argues that AROV means wolves that hunt nocturnally, citing Yirmiyah 5:6 and Tzefania 3:3 for support. [The reader is encouraged to see the summary of the various views on AROV in “The Living Torah” by R. Aryeh Kaplan.]

Ramban notes that Hashem’s instruction to Moshe to confront Pharaoh at the water in the early morning precedes three plagues: DAM (blood), AROV and BARAD (hail). This is because each one begins a grouping of plagues, in accordance with the teaching that we quote in the Passover Haggadah:
“R. Yehudah used to assign them symbols: DeTZa”CH, AdaSH, BeACHa”V.”

In addition, each of these plagues will bring much death to the Egyptians. So, says Ramban, when Pharaoh goes out to the water, a large entourage will accompany him who will hear Moshe’s dire warning. They will then be in a position either to implore Pharaoh to relent, or, if they do not, to deserve punishment as well.

No one protests, and so the AROV comes as punishment for making the Hebrews go out to trap wild animals for the Egytians’ amusement in zoos and circuses (Shemot Rabat 11:3).

And Pharaoh called for Moshe and Aharon and said, “Go, sacrifice to your G-d in the land.”

And Moshe said, “It is not proper to do so, because the “abomination of (TO’AVAT) Egypt” shall we sacrifice to Hashem, our G-d. Behold, if we sacrifice the “abomination of Egypt” before their eyes, shall they not stone us? A distance of three days shall we go in the desert, and we will sacrifice to Hashem, our G-d as He will tell us” (vs. 21-23).

By “abomination,” Moshe either means that sacrificing animals sacred to the Egyptians is objectionable (Rashi), or that sheep and goats are repulsive to them (Rashbam) or that, at the time, Moshe said “god of the Egyptians,” but changed it here, in order to degrade idolatry in the Torah (Ibn-Ezra).

And Pharaoh said, “I will release you and you will sacrifice to Hashem, your G-d in the desert. Only, do not go too far. Entreat on my behalf.”

And Moshe said, “Behold I am going to leave you, and I will entreat Hashem, and tomorrow the AROV will depart from Pharaoh, his servants and his nation. Only, let Pharaoh not continue to trifle by not releasing the people to sacrifice to Hashem” (vs. 24-27).

Moshe prays for the AROV to depart, rather than die (as happened with frogs), so the Egyptians would not benefit from the skins of AROV, whereas with frogs there was no such use (Shemot Rabat 11:4). He reminds Pharaoh not to repeat his disingenuous behavior after the plague of frogs.

And Moshe left Pharaoh, and he entreated Hashem. And Hashem did according to the word of Moshe, and the AROV departed from Pharaoh, his servants and his nation; not one remained. But Pharaoh made his heart stubborn even this time, and he did not release the people (vs. 26- 28).

AROV does not involve a transformation of nature, as occurred with the previous trio of plagues. Instead, it shows that the forces of nature, created by Hashem, are in constant need of His control: by releasing His restraining Hand, the AROV will attack (MASHLIACH). Furthermore, by keeping the AROV out of Goshen, Hashem demonstrates that His influence in the world is constant; He decides where the harmful forces of the universe will function, and where they will not. In the first group of plagues, Hashem showed that He is the world’s Creator; now, He shows that He is also its Guide and Sustainer.

The plague of AROV features man’s different uses and abuses of those of Hashem’s creations that are most like man: the animal kingdom. Animals, which represent the raw forces of nature, can be made abominable through idolatry, or sanctified to the Glory of Hashem.