Reserved Mitzvos

We know that the mitzvos of tzitzis and tefillin are applicable the entire day. This leads us to the question as to why we wear them particularly only during shacharis.

The Meshech Chochma cites the gemara that in the merit of Avraham saying אם מחוט ועד שרוך נעל, that he would refrain from taking the spoils of Sedom, his children were merited the mitzvos of tzitzis and tefillin. Now, the gemara elsewhere tells us that Avraham instituted shacharis. Consequently, since shacharis is Avraham’s tefilla, and because tzitzis and tefillin are in his merit, we have the practice to specifically wear them during shacharis.