Based on this question, Shulchan Aruch (O"C 34:2-3) says that only people who are noted for their piety should put on Rabbeinu Tam tefillin. Why do Lubavitcher chasidim (and descendants of certain ...
I have heard that the baal haTanya put on his t'fila shel yad while seated (as S'faradim do). Does anyone have a source for this (or for the opposite: that he put on his shel yad standing)? If he ...