The principle of אין מעבירין על המצוות which we discussed, also forbids passing over the tefillin shel yad or tefillin shel rosh in order to first take the other. Therefore, one must arrange his tefillin in such a way that he first encounters the one that he plans to wear first, namely, the tefillin shel yad. In presenting the obligation of tefillin, the Torah first mentions the shel yad (וקשרתם לאות על ידיך) and only then the shel rosh (והיו לטוטפות בין עיניך) , indicating that one must first don the shel yad before the shel rosh. As such, one must ensure that he first encounters the shel yad before the shel rosh, so that he will not be in a situation requiring him to “pass over” the shel rosh in favor of the shel yad.[40]

1) The tefillin shel yad and tefillin shel rosh should be positioned in the tefillin bag one beside the other. In order to ensure to always first remove the shel yad before the shel rosh, one should accustom himself to always position the shel yad on the same side, either to the right or to the left.[41]

a. Preferably, one should position the shel yad on the right side and a bit higher than the shel rosh, in order

to further assure that he will always remove the shel yad before the shel rosh.[42]

b. One who uses a long, narrow tefillin bag (as opposed to the more common short, wide bags) must ensure to place the tefillin shel rosh inside the bag before the tefillin shel yad, so that he will always remove the shel yad first.

Furthermore, one should preferably not remove the shel yad from his arm until the shel rosh has been placed in the bag, thereby guaranteeing that the shel yad is always positioned near the opening of the bag.[43]

c. If one keeps his shel yad and shel rosh in two different bags, he must clearly label the bags so that they are always used for the same tefillin. Since the sanctity of the shel rosh exceeds that of the shel yad, it is improper to place the shel yad in the bag designated for the shel rosh. If the two bags are kept together in a larger bag, the bag of the shel yad should be positioned a bit higher than that of the shel rosh, so that one will always remove the tefillin shel yad before the tefillin shel rosh.[44]

2) If a person keeps his tefillin Rashi and tefillin Rabbenu Tam together in a large bag (in which he keeps also his tallit and siddur), he must ensure that the tefillin Rashi are always positioned on the same side, so that he will always remove them first. If one mistakenly removed his tefillin Rabbenu Tam before tefillin Rashi, he should nevertheless first don the tefillin Rashi.[45]