Why don’t you recite the blessing shehekhiyanu (שֶהֶחֱיָינוּ) the first time you don tefillin? TB Menakhot 75

Today’s daf TB Menakhot 75 explains when we say the blessing before we observe a mitzvah for the first time and when we don’t. “Rav Yosef said: From where do I say this halakha? (If a cooked dish contains pieces of bread there the size of an olive-bulk  like challah kugel and matza brei one recites the blessing hamotzi. Otherwise if the cooked dish contains less than an olive-bulk pieces of bread, one recites the blessing borai menai mezanot, בּוֹרֵא מִינֵי מְזוֹנוֹת.-gg)  “As it is taught in a baraita: The first time an Israelite would stand and instruct a priest to sacrifice meal offerings in Jerusalem on his behalf, he would recite: (shehekhiyanu (שֶהֶחֱיָינוּ) Blessed are You, Lord our God, King of the universe, Who has given us life and sustained us and brought us to this time, as it is the first time that the Israelite fulfills the mitzva of bringing that offering. Following the removal of the handful, when the priest would take the meal offerings in order to eat them, he would first recite the blessing of: Who brings forth bread from the earth. And we learned in the mishna: And in all meal offerings that are broken into pieces, the priest breaks them into pieces the size of an olive-bulk. This proves that over pieces of bread that are the volume of an olive-bulk, one recites the blessing of: Who brings forth bread from the earth.” (Sefaria.com translation)

Why should one recite the blessing shehekhiyanu (שֶהֶחֱיָינוּ) when offering the minkha for the first time, but not the first time the child dons teffilin? Both are mitzvot!

Note 23 concerning this passage on our daf in the Schotenstein explains the difference.

“(The blessing of shehekhiyanu (שֶהֶחֱיָינוּ) is a prayer of thanksgiving to God for having brought one to a particular occasion, such as the performance of a mitzvah that comes at a certain time.) The Baraita teaches that it is recited by a Kohen when he offers a minkha-provided that he has not yet brought a minkha that year…

“Tosafot explain that the Kohanim were divided into mishmarot that served in the Temple one week at a time on a rotating basis. The number of mishmarot was 24, allowing for the rotation to begin anew twice a year. Every mishmar was divided into batei av (a family), each of which served for one day of the week. An individual Kohen would serve as a member of his beit av only one day and every six months. When a Kohen offered a minkha or animal offering for his first time on the day assigned to his beit av, he will recite the shehekhiyanu (שֶהֶחֱיָינוּ), as one does before performing a mitzvah that is limited to a particular date, e.g. shofar and lulav.”

The donning of tefillin isn’t limited to a particular date; consequently, the first time somebody puts on tefillin s/he doesn’t recite the blessing shehekhiyanu (שֶהֶחֱיָינוּ) Any day except Shabbat and holidays is always a good day to don tefillin!