Exodus 8:15

And the astrologers said to Pharoh, This is not by the power or strength of Mosheh and Aharon; but this is a plague sent from before the Lord. Yet the design of Pharoh's heart was strengthened, and he would not hearken to them, as the Lord had said.

And the magicians said: Since they saw that they did like Aaron's act with the snake and with the plagues of blood and frogs, but they could not do now like what Aaron did; they said to Pharaoh, "This plague did not come on account of Israel, that you should send them away. Rather, it is a plague of God, according to the system of the stars, upon the constellation of Egypt... Moreover, since Moses had given word to Pharaoh about the plague of the Nile before it occurred, as well as the plague of the frogs; but the did not mention the plague of the lice beforehand.

AND THE MAGICIANS SAID UNTO PHARAOH: THIS IS THE FINGER OF G-D. Rabbi Abraham ibn Ezra commented that because the magicians had done as Aaron did with the serpent and also with the plagues of blood and the frogs and now they could not do so, they therefore said to Pharaoh: “This plague of gnats has not come through Aaron for the sake of Israel. Rather it is a plague of G-d due to the particular [evil] stars under which the land of Egypt found itself at the time.” Pharaoh did not deny the existence of the Creator 5:3. but only the Divine Name which Moses mentioned to him. This is similar in sense to the verse, It was not His hand that smote us; it was a chance that happened to us. Therefore Pharaoh’s heart was hardened. And Ibn Ezra brought proof for his explanation from the fact that Scripture does not state that the magicians said, “This is the finger of the Eternal,” which would have been a reference to the G-d of Israel, just as Pharaoh said to Moses and Aaron, Entreat the Eternal. Another proof [which Ibn Ezra brought for his explanation] is that in the case of the smiting of the river, Moses had forewarned Pharaoh,, Verses 27-29). but he mentioned nothing to him about the plague of gnats. [Therefore the magicians felt justified in saying that it was not a plague for the sake of Israel but merely due to the evil stars.]
Ibn Ezra’s interpretation does not appear to me to be correct. “A chance” is not called “the finger of G-d.” Only a plague which comes directly from Him as a form of punishment is called the hand of the Eternal and the finger of G-d, just as it is written in the verse which [Ibn Ezra] mentioned: It was not His hand that smote us. And it is furthermore written: And Israel saw the great hand; And the hand of the Eternal shall be against you;, 5:11. the hand of G-d was very heavy there., 5:11. Moreover, in the next plague of swarms, as well as in the following ones, Pharaoh no longer called upon the magicians to stand before Moses to do the same things, even though there had been a forewarning of their coming!
But the subject, in accordance with the simple explanation of Scripture, is as follows: When the magicians saw that they could not bring forth the gnats, they admitted Aaron’s deed to be through an act of G-d, and this is why Pharaoh no longer called upon them from that time on. They [the magicians] said, This is ‘the finger’ of G-d, and not “the …

אצבע אלוקים הוא, this is a natural disaster [the word אל-הים equaling 86 numerically, the same as הטבע=“nature” Ed.] They denied that this plague, which had not been advertised beforehand, was the work of Moses and Aaron whom they had considered superior sorcerers, but had been orchestrated by the god of nature. They argued that if this had been a work of sorcerers they too could have duplicated the phenomenon.