עקידת יצחק — שמע ישראל / ואהבת את ה' אלהיך בכל לבבך

Q — Why is Shema to be recited and repeated continually — "when you sit, when you walk, when you lie down and rise"? Why bind it with tefillin and mezuzah? Why is love of God commanded, as if love can be ordered?

A — The constant recitation and the physical mitzvos exist to fix the emunah of God's unity permanently in the heart, for that conviction is the foundation of everything. Love of God is commandable because it follows inevitably from sustained contemplation of His oneness — the mind directed again and again to the truth of "ה' אחד" generates the love. Tefillin and mezuzah surround a person with reminders so the yesod never lapses; the whole apparatus serves to keep the unity of God continuously present and alive within.