Biblical Commentary on the Old Testament, by Carl Friedrich Keil and Franz Delitzsh, [1857-78], at sacred-texts.com
The plague of Frogs, or the second plague, also proceeded from the Nile, and had its natural origin in the putridity of the slimy Nile water, whereby the marsh waters especially became filled with thousands of frogs. צפרדּע is the small Nile frog, the Dofda of the Egyptians, called rana Mosaica or Nilotica by Seetzen, which appears in large numbers as soon as the waters recede. These frogs (הצּפרדּע in Exo 8:6, used collectively) became a penal miracle from the fact that they came out of the water in unparalleled numbers, in consequence of the stretching out of Aaron's staff over the waters of the Nile, as had been foretold to the king, and that they not only penetrated into the houses and inner rooms ("bed-chamber"), and crept into the domestic utensils, the beds (מטּה), the ovens, and the kneading-troughs (not the "dough" as Luther renders it), but even got upon the men themselves.
This miracle was also imitated by the Egyptian augurs with their secret arts, and frogs were brought upon the land by them. But if they were able to bring the plague, they could not take it away. The latter is not expressly stated, it is true; but it is evident from the fact that Pharaoh was obliged to send for Moses and Aaron to intercede with Jehovah to take them away. The king would never have applied to Moses and Aaron for help if his charmers could have charmed the plague away. Moreover the fact that Pharaoh entreated them to intercede with Jehovah to take away the frogs, and promised to let the people go, that they might sacrifice to Jehovah (Exo 8:8), was a sign that he regarded the God of Israel as the author of the plague. To strengthen the impression made upon the king by this plague with reference to the might of Jehovah, Moses said to him (Exo 8:9), "Glorify thyself over me, when I shall entreat for thee," i.e., take the glory upon thyself of determining the time when I shall remove the plague through my intercession. The expression is elliptical, and לעמר (saying) is to be supplied, as in Jdg 7:2. To give Jehovah the glory, Moses placed himself below Pharaoh, and left him to fix the time for the frogs to be removed through his intercession.
The king appointed the following day, probably because he hardly thought it possible for so great a work to be performed at once. Moses promised that it should be so: "According to thy word (sc., let it be), that thou mayest know that there is not (a God) like Jehovah our God." He then went out and cried, i.e., called aloud and earnestly, to Jehovah concerning the matter (דּבר על) of the frogs, which he had set, i.e., prepared, for Pharaoh (שׂוּם as in Gen 45:7). In consequence of his intercession God took the plague away. The frogs died off (מן מוּת, to die away out of, from), out of the houses, and palaces, and fields, and were gathered together by bushels (חמרים from חמר, the omer, the largest measure used by the Hebrews), so that the land stank with the odour of their putrefaction. Though Jehovah had thus manifested Himself as the Almighty God and Lord of the creation, Pharaoh did not keep his promise; but when he saw that there was breathing-time (רוחה, ἀνάψυξις, relief from an overpowering pressure), literally, as soon as he "got air," he hardened his heart, so that he did not hearken to Moses and Aaron (והכבּד inf. abs. as in Gen 41:43).
The Gnats, or the third plague. - The כּנּם, or כּנּים (also כּנּם, probably an old singular form, Ewald, 163f), were not "lice," but σκνῖφες, sciniphes, a species of gnats, so small as to be hardly visible to the eye, but with a sting which, according to Philo and Origen, causes a most painful irritation of the skin. They even creep into the eyes and nose, and after the harvest they rise in great swarms from the inundated rice-fields. This plague was caused by the fact that Aaron smote the dust of the ground with his staff, and all the dust throughout the land of Egypt turned into gnats, which were upon man and beast (Exo 8:17). "Just as the fertilizing water of Egypt had twice become a plague, so through the power of Jehovah the soil so richly blessed became a plague to the king and his people."
"The magicians did so with their enchantments (i.e., smote the dust with rods), to bring forth gnats, but could not." The cause of this inability is hardly to be sought for, as Knobel supposes, in the fact that "the thing to be done in this instance, was to call creatures into existence, and not merely to call forth and change creatures and things in existence already, as in the case of the staff, the water, and the frogs." For after this, they could neither call out the dog-flies, nor protect their own bodies from the boils; to say nothing of the fact, that as gnats proceed from the eggs laid in the dust or earth by the previous generation, their production is not to be regarded as a direct act of creation any more than that of the frogs. The miracle in both plagues was just the same, and consisted not in a direct creation, but simply in a sudden creative generation and supernatural multiplication, not of the gnats only, but also of the frogs, in accordance with a previous prediction. The reason why the arts of the Egyptians magicians were put to shame in this case, we have to seek in the omnipotence of God, restraining the demoniacal powers which the magicians had made subservient to their purposes before, in order that their inability to bring out these, the smallest of all creatures, which seemed to arise as it were from the dust itself, might display in the sight of every one the impotence of their secret arts by the side of the almighty creative power of the true God. This omnipotence the magicians were compelled to admit: they were compelled to acknowledge, "This is the finger of God." "But they did not make this acknowledgment for the purpose of giving glory to God Himself, but simply to protect their own honour, that Moses and Aaron might not be thought to be superior to them in virtue or knowledge. It was equivalent to saying, it is not by Moses and Aaron that we are restrained, but by a divine power, which is greater than either" (Bochart). The word Elohim is decisive in support of this view. If they had meant to refer to the God of Israel, they would have used the name Jehovah. The "finger of God" denotes creative omnipotence (Psa 8:3; Luk 11:20, cf. Exo 31:18). Consequently this miracle also made no impression upon Pharaoh.
As the Egyptian magicians saw nothing more than the finger of God in the miracle which they could not imitate, that is to say, the work of some deity, possibly one of the gods of the Egyptians, and not the hand of Jehovah the God of the Hebrews, who had demanded the release of Israel, a distinction was made in the plagues which followed between the Israelites and the Egyptians, and the former were exempted from the plagues: a fact which was sufficient to prove to any one that they came from the God of Israel. To make this the more obvious, the fourth and fifth plagues were merely announced by Moses to the king. They were not brought on through the mediation of either himself or Aaron, but were sent by Jehovah at the appointed time; no doubt for the simple purpose of precluding the king and his wise men from the excuse which unbelief might still suggest, viz., that they were produced by the powerful incantations of Moses and Aaron.
The fourth plague, the coming of which Moses foretold to Pharaoh, like the first, in the morning, and by the water (on the bank of the Nile), consisted in the sending of "heavy vermin," probably Dog-Flies. ערב, literally a mixture, is rendered κυνόμυια (dog-fly) by the lxx, πάμμυια (all-fly), a mixture of all kinds of flies, by Symmachus. These insects are described by Philo and many travellers as a very severe scourge (vid., Hengstenberg ut sup. p. 113). They are much more numerous and annoying than the gnats; and when enraged, they fasten themselves upon the human body, especially upon the edges of the eyelids, and become a dreadful plague. כּבד: a heavy multitude, as in Exo 10:14; Gen 50:9, etc. These swarms were to fill "the houses of the Egyptians, and even the land upon which they (the Egyptians) were," i.e., that part of the land which was not occupied by houses; whilst the land of Goshen, where the Israelites dwelt, would be entirely spared. הפלה (to separate, to distinguish in a miraculous way) is conjugated with an accusative, as in Psa 4:4. It is generally followed by בּין (Exo 4:4; Exo 11:7), to distinguish between. עמד: to stand upon a land, i.e., to inhabit, possess it; not to exist, or live (Exo 21:21).
"And I will put a deliverance between My people and thy people." פּדוּת does not mean διαστολή, divisio (lxx, Vulg.), but redemption, deliverance. Exemption from this plague was essentially a deliverance for Israel, which manifested the distinction conferred upon Israel above the Egyptians. By this plague, in which a separation and deliverance was established between the people of God and the Egyptians, Pharaoh was to be taught that the God who sent this plague was not some deity of Egypt, but "Jehovah in the midst of the land" (of Egypt); i.e., as Knobel correctly interprets it, (a) that Israel's God was the author of the plague; (b) that He had also authority over Egypt; and (c) that He possessed supreme authority: or, to express it still more concisely, that Israel's God was the Absolute God, who ruled both in and over Egypt with free and boundless omnipotence.
This plague, by which the land was destroyed (תּשּׁחת), or desolated, inasmuch as the flies not only tortured, "devoured" (Psa 78:45) the men, and disfigured them by the swellings produced by their sting, but also killed the plants in which they deposited their eggs, so alarmed Pharaoh that he sent for Moses and Aaron, and gave them permission to sacrifice to their God "in the land." But Moses could not consent to this restriction. "It is not appointed so to do" (נכון does not mean aptum, conveniens, but statutum, rectum), for two reasons: (1) because sacrificing in the land would be an abomination to the Egyptians, and would provoke them most bitterly (Exo 8:26); and (2) because they could only sacrifice to Jehovah their God as He had directed them (Exo 8:27). The abomination referred to did not consist in their sacrificing animals which the Egyptians regarded as holy. For the word תּועבה (abomination) would not be applicable to the sacred animals. Moreover, the cow was the only animal offered in sacrifice by the Israelites, which the Egyptians regarded as sacred. The abomination would rather be this, that the Iran would not carry out the rigid regulations observed by the Egyptians with regard to the cleanness of the sacrificial animals (vid., Hengstenberg, p. 114), and in fact would not observe the sacrificial rites of the Egyptians at all. The Egyptians would be very likely to look upon this as an insult to their religion and their gods; "the violation of the recognised mode of sacrificing would be regarded as a manifestation of contempt for themselves and their gods" (Calvin), and this would so enrage them that they would stone the Israelites. The הן before נזבּח in Exo 8:26 is the interjection lo! but it stands before a conditional clause, introduced without a conditional particle, in the sense of if, which it has retained in the Chaldee, and in which it is used here and there in the Hebrew (e.g., Lev 25:20).
These reasons commended themselves to the heathen king from his own religious standpoint. He promised, therefore, to let the people go into the wilderness and sacrifice, provided they did not go far away, if Moses and Aaron would release him and his people from this plague through their intercession. Moses promised that the swarms should be removed the following day, but told the king not to deceive them again as he had done before (Exo 8:8). But Pharaoh hardened his heart as soon as the plague was taken away, just as he had done after the second plague (Exo 8:15), to which the word "also" refers (Exo 8:32).