Shulchan Aruch: Chapter 29 - [Not to Recite a Blessing when Removing Tefillin]

SECTION 29 [Not to Recite a Blessing when Removing Tefillin]. (1)

1 No blessing should be recited when removing tefillin.1 [This applies] even when one takes them off on Friday afternoon before sunset,2 at which time one is obligated to take them off because Shabbos and festivals are not days on which tefillin [should be worn]. [Indeed,] when one wears [tefillin at that time] with the intent of fulfilling the mitzvah, one transgresses the prohibition against adding to the Torah’s commandments.3

Nevertheless, [taking off the tefillin at such times] does not warrant the recitation of a blessing. For if one would continue wearing tefillin [on Shabbos or a festival] without intending to fulfill a mitzvah, one would not be transgressing a Scriptural prohibition; [one is required to remove the tefillin] only because of a Rabbinic prohibition, lest one [inadvertently] go out to the public domain while wearing them, as explained in sec. 31.4 Thus removing tefillin is not a mitzvah in its own right, and is necessary only because of the Rabbinic decree.

Needless to say, this applies [to any other day] during the week, when one removes the tefillin a short time before sunset. Then one should surely not recite a blessing, for [in principle] the night is a time when tefillin may be worn and there is no need to remove them. Nevertheless, as explained in sec. 30[:1-2, this law] should not be taught [as a directive for the public].