There are four perashiot (paragraphs written on leather parchments) inside Tefillin boxes. The same four appear both in the Tefillin that are placed on the head and the one on the arm. These perashiot speak about central concepts in Judaism.
The first perasha of “Kadesh li” discusses the freedom from slavery in Egypt. Two of the four sons from the Passover Seder are found in these paragraphs. The second perasha of “Vehaya Ki Yevi’acha” speaks about the plague of the first born of Egypt. The death of the first born of Egypt, in addition to redeeming of out first-born sons and animals, actuate a rejection of the strengths of idolatry and magical powers. The first born of the Egyptian as well as those of other nations were priests. The sanctity of the first born within Judaism is actually a rejection of idolatrous beliefs.
The final two paragraphs that are written in the tefillin are the most famous in Judaism. They are the first two paragraphs of “Shema Yisrael”. The portion of “Shema Yisrael” speaks about the Unity of the Blessed Creator and loving him. The final perasha is “Vehaya im Shmo’a”. It discusses Devine Providence and heavenly reward and punishment.
There is a distinct relationship between these four perashiot. They all mention the importance of study and internalization of these subjects. Additionally, educating children in these particular subjects is mandatory. One needs to constantly teach them to his children and even more so during the Passover Seder.