According to the RASBA can someone actually put on tefillin over his shirt?Could you explain the shita?
Answer:
Yes, there is indeed a dispute among Rishonim over this point, and according to the Rashba (282) the principles of chatzitzah don’t apply to Tefillin.
The reason for this is that the Tefillin are considered to be “upon your arm” even if this is done over a shirt or other element (the Rashba writes that the laws of Tefillin cannot be equated to the status of the Kohen Gadol vis-a-vis the Tzitz).
However, the halachah follows the opinion of the Rosh (Tefillin 18), and therefore one must be careful of a partition between Tefillin and arm.
Best wishes.
