The Torah describes the mitzvah of the arm Tefilin as an action ("you shall bind them... on your arm") whereas the mitzvah of the head Tefilin is described as a state of being ("they should be... on your head.") What is the legal and mystical distinction between these two expressions? What does it teach us about the difference between the mind and the heart?

Based on Likkutei Sichos, vol. 39, pp. 22-29.