The final aliyah of Parshas Bo addresses the mitzvos of Pesach as well as the sanctification of the firstborn. The commandment of tefillin is also woven into the text which contains these mitzvos. Why is tefillin of special relevance at this point and in this context?

It is well-known that tefillin shel yad (the tefillin which is placed on the arm) represents submission of one's strength and might to Hashem's service; this is why the bayis (box) of tefillin shel yad goes directly on the biceps muscle. Tefillin shel rosh (the tefillin which is worn on the head) symbolizes the commitment and subservience of one's mind to Hashem's Will, as indicated by the location where tefillin shel rosh is worn.

Thus, tefillin reflect our essential role as Jews insomuch as they tangibly designate us as servants of Hashem regarding both our physcial and intellectual capacities. This theme is identical with that of the mitzvos of Pesach and the laws of the firstborn, as these commandments display our attachment and comphrehensive devotion to Hashem as His direct and close servants after being released from bondage to Pharaoh. This is why the Torah presents the mitzvah of tefillin together with the mitzvos of Pesach and the laws of the firstborn.

We were liberated from Mitzrayim and acquired by Hashem, elevated and sanctified for direct service to Him. Tefillin are a brand of servitude to Hashem, and they thus eternally complement the attachment and total devotion to Him and His service as expressed by Pesach and the sanctification of the firstborn. This is why tefillin are presented by the Torah in conjunction with these mitzvos.