When it comes to determining the order in which different things happen, there are often rules. According to Zevachim 89a, there are two rules in particular:
- That which occurs more frequently takes precedence (כל התדיר מחברו קודם את חברו);
- That which is more sacred takes precedence (כל המקודש מחברו קודם את חברו).
When it comes to the relative order of tallit and tefillin every morning, the rule is that one puts on the tallit and only then puts on the tefillin. This is because the tallit is put on every morning, while the tefillin is only worn on non-festive weekdays. In the words of the Kitzur Shulchan Arukh (10:2):
והא דמקדימין את הציצית לתפילין, משום שמצוות ציצית תדירה יותר, שנוהגת בין בחול, בין בשבת ויום טוב, ומצות תפילין אינה נוהגת אלא בחול, וקימא לן תדיר ושאינו תדיר, תדיר קודם
The reason that we precede the tefillin with the tzitzit is because the tzitzit are worn more frequently, since they are used by weekdays, shabbatot and festivals, while tefillin are only used on [non-festive] weekdays. We have a principle that when one thing is more frequent than another, the frequent takes precedence.
However, the Shulchan Arukh also explicitly states (Orach Chayim 25:1) that we put on tefillin after the tallit because of the principle that we should ascend in holiness (מעלין בקודש), which indicates that while the mitzva of tzitzit might be more frequently observed than the mitzva of tefillin, tefillin have greater sanctity.
So, why do we apply rule 1), that an object used more frequently than another takes precedence over it and not rule 2), that the object with greater sanctity takes precedence? Cannot rule 2) be used in order to prioritise tefillin over tzitzit?