In the runup to the Exodus, there is a commandment that seems to come out of left field, concerning the tefillin that Jewish men wear on their arms and forehead:
“And this shall serve you as a sign on your hand and as a reminder between your eyes—in order that the Teaching of G-d may be in your mouth—that with a mighty hand G-d freed you from Egypt. (E. 13:9)
This is followed shortly after by the commandment that:
You shall set apart for G-d every first issue of the womb: every male firstling that your cattle drop shall be G-d’s. … And you must redeem every male first-born among your children. (E. 13:12)
And when, in the future a child of yours asks you, saying, ‘What does this mean?’ you shall reply, ‘It was with a mighty hand that G-d brought us out from Egypt, the house of bondage. (E. 13:14)
And then, a few verses later, the Torah reminds us again of the sign on our hands, and between our eyes:
“And so it shall be as a sign upon your hand and as a symbol between your eyes that with a mighty hand G-d freed us from Egypt.” (E. 13:16)
What on earth connects all these ideas? Why does the Torah put them together in this way, and at this time?
Firstly, we need to appreciate that Egypt was the oldest civilization – they saw themselves as the first-borns of the world. First-borns were always supposed to be special, to inherit. In that world, there is an iron-clad hierarchy to be found in the natural world. And each animal “naturally” can procreate.
And so the Exodus was an attack on Egypt and on all these ideas. The Exodus tells us that G-d trumps nature.
So the tefillin are a way to answer the question our child will ask: “How am I supposed to understand this?”
We answer that we are to see G-d’s hand in everything in the world. So we are to wear signs between the eyes (to guide what we think we see, and how we think), and our arms (to remember that strength and all physical performance comes from G-d, not from our own arms). Any story can be told different ways: the Torah wants us to tell the story in such a way that we appreciate that G-d’s power fills our world.
This is why we are commanded to have the signs on our hands, and between our eyes – our perceptions, our understandings (the eyes) are to always remind us that G-d’s hand took us out of Egypt, and can thus do anything. There is nothing in the physical, animal world that is somehow outside of the reach of G-d’s (symbolic) hand – which is why we wear the signs on our hands. And we are always to see G-d’s role in this world: we keep Him between our eyes as a prism through which we are to understand the world.
We wear tefillin, the signs on our hand and between our eyes, to help us symbolically connect to these core ideas.
P.S. None of this is meant to replace or degrade other explanations for the tefillin. There are multiple facets for any symbolic law, each able to teach us another lesson.