Once only Chassidim and Sefardim wore Rabbeinu Tam Tefillin, and Chabad Chassidim seldom wore them before age 18—a custom that the Rebbe overturned in 1966 with a landmark Sicha that called on every Jewish man from any background to begin wearing Rabbeinu Tam Tefillin starting from Bar Mitzvah. This two-part series explores the factors that contributed to this shift and its modern implications, through letters and Sichos.

Part II: The Rebbe's 1966 Rabbeinu Tam Tefillin initiative; Responding to those who claim it is not their custom; Reb Moshe Feinstein joins the initiative