Likutei Halakhot, Orach Chaim, Laws of Phylacteries 5:10/ליקוטי הלכות·אורח חיים·הלכות תפילין ה׳:י׳

1And all this is the aspect of tefillin, which are the above-mentioned aspect of Arikhath Apayim, which is the aspect of the new brains and vitality that we draw by the mitzvah of tefillin, from the elders in sanctity who receive from the highest elder who is the blind one.