Reference for Eruvin 190:16

אלא כדאמר רב שמואל בר רב יצחק מקום יש בראש שראוי להניח בו שתי תפילין הכא נמי מקום יש ביד שראוי להניח בו שתי תפילין

and binds them on his arm.<span class="x" onmousemove="('comment',' As in this manner one would on a weekday wear two tefillin on his arm, a similar number was also allowed on the Sabbath for the purposes of saving.');">²⁹</span> It might still be contended, that R'Huna only intended that they should not be treated with disrespect;<span class="x" onmousemove="('comment',' So that they be not crushed by the bundle.');">²⁸</span> did he, however, say that it<span class="x" onmousemove="('comment',' I.e., the wearing of two tefillin on one's arm.');">³⁰</span>

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