Exode 8:18

And I will do wonders that day in the land of Goshen where My people dwell, that there no swarms of wild beasts shall be; - that thou mayest know that I the Lord am the Ruler in the midst of the land.

AND I WILL SET APART IN THAT DAY THE LAND OF GOSHEN. Due to the fact that the first plagues were not migratory in nature, it was no wonder that they were confined to the land of Egypt and were not to be in the land of Goshen, [Israel’s habitation]. But this [plague of swarms] was a migratory plague. Thus when the wild beasts came up from the lions’ dens, from the mountains of the leopards, and brought ruin upon the whole land of Egypt, it was natural that they also come into the land of Goshen, which contained some of the best of the land of Egypt. of Egypt. Therefore it was necessary for Him to say, And I will set apart in that day the land of Goshen, so that it would be completely saved [from the wild beasts] because My people dwell in it, as the majority of its inhabitants were Israelites.
And I will put ‘p’duth’ (a division) between My people and thy people. The intent thereof is that even in the land of Egypt, if the beasts will find a certain Jew, they will not harm him. Instead they will devour the Egyptians, as it is written: He sent among them swarms of beasts, which devoured them. This is the sense of the word ‘p’duth’ between My people and thy people, which is similar to the verse, I have given Egypt as thy ransom, Ethiopia and Seba for thee.

I AM THE ETERNAL IN THE MIDST OF THE EARTH. Rabbi Abraham ibn Ezra explained it as being a figure of speech, emblematic of the nature of kings to establish their seat of government in the center of the kingdom in order to be near to the remote comers thereof. This explanation makes no sense. Rather, its intent is to state that He rules and supervises in the midst of the earth, and not, as some think, that thick clouds are a covering to Him, that He seeth not; and He walketh in the circuit of heaven. It is possible that the sense of the expression is similar to the verse, For My name is in him, and the secret thereof is sublime and recondite.

והפלאתי ביום ההוא, seeing that these wild beasts are fleet-footed and would invade any kingdom without regard to international borders once the plague has been released, the Torah had to stress that it would be observed that these animals would respect the unfenced areas in which the Jews were living as if they were physical obstacles. The same phenomenon would be observed when the “natural” disaster which struck the herds under the heading of דבר, the fifth plague, did not infect a single animal owned by the Israelites.