In the Haftarah of the Torah portion of Bo, the Prophet Jeremiah compares Egypt to two different living creatures: a calf and a snake. "Egypt is a beautiful calf... Its mercenaries are also like fatted lambs... Its voice will ring out like a snake." [46:20-22].
The comparison of Egypt to a snake corresponds to the link between this nation and the primordial serpent which caused Adam to sin. The serpent in Genesis represents natural intellect, which is convoluted, earthy and deadly. In itself it is not evil (note that the sages said that the evil inclination rode on the back of the serpent but not that the serpent is the evil inclination itself), but it does not have the ability to rise up to the moral heights that come as a result of the awareness of free choice.
Egypt, like the serpent, is nothing other than a wonderful improvement over the traits of raw nature. The Nile River, the great force of nature, which brings water to the arid desert, relieves the Egyptians not only of any worries about famine but also of the need for prayer. This is the opposite of the Land of Israel, which "will drink water from the rain of the sky" [Deuteronomy 11:11], with a need for the prayers and the high moral status of mankind.
Egypt did not understand the concept of freedom – not freedom of man, not freedom in the political system, and not the freedom of the laws of nature. In the era of Joseph, the magicians of Egypt could not imagine any change in the natural situation of Egypt that would lead to a famine. And that is why the dynasty of the Pharaohs in Egypt placed a snake on the same spot of the head where we wear tefillin, symbolizing the subjugation of mankind to the laws of nature. The cycle is also a trait of nature, and it is symbolized by the calf, whose foot is round, and which is "in the form of an ox that eats grass" [Psalms 106:20]. (In Hebrew the word for calf is "eigel," from a root similar to the word for a cycle, "ma'agal.") The ox bows its head down towards the earth which provides it with its food, as opposed to man, who lifts his food up to his mouth. The serpent is also characterized by its cyclic shape, another symbol of the constant cycling of nature.
As opposed to the serpent, the Torah commands us to put at the tops of our faces square boxes with straight lines, which are an indication of a moral system which has upward and downward directions and various levels of moral values. The boxes of the tefillin carry in them a summary of our knowledge of transcendental revelation, which is expressed in the powerful hand of the redemption from Egypt and from its mental and natural limits.
The straps of the tefillin, which can be made from the leather of a calf, show that we can rise above the level of the calf and that it can be a useful tool to represent the contents of the tefillin.
The symbolism of Egypt also hints at two different sequences of the four passages from the Torah that are placed in the tefillin, one according to the opinion of Rashi and the other according to the opinion of Rabeinu Tam. Archeological excavations in Egypt have revealed the death mask of the mummy of the Pharaoh Tutankhamun, and on his forehead there is a double symbol. There are a vulture and a snake, which according to the Kabbalah correspond to the "spheres" of understanding and royalty, representing this world and the next, and this is related to the roots of the dispute between the two rabbis about the sequence in the tefillin. This is an example of the deep-seated principle that the external shell (Egypt) comes before the fruit (Israel).
Source: Shabbat-B’Shabbato (http://www.zomet.org/eng), Bo 5775, Issue Number 1559.