1) One recites the berachah over tefillin every time he puts them on during the day; thus, for example, those who wear tefillin during minhah on a fast day recite the berachah at minhah just as they do at shaharit.73 (We refer here to somebody who wears a different pair of tefillin Rashi; the halachot pertaining to tefillin Rabbenu Tam are addressed in the chapter “Tefillin Rabbenu Tam.”)

a. However, if one removes his tefillin with the intention of wearing them again immediately thereafter, he does not recite a new berachah, provided that his mind was not distracted from his tefillin in the interim.[74]

b. There is a dispute among the halachic authorities regarding one who removes his tefillin to use the restroom and then puts them back on after leaving the restroom. Whereas some require reciting the berachah as usual75, others maintain that in this case one should omit the phrase ה' אלוקינו מלך העולם in the berachah, and should think this phrase in his mind without verbalizing it.[76] One should consult his Rabbi for guidance in this regard.

2) If one removed his tefillin in order to wear a different pair of tefillin, he must recite a new berachah over the second pair.[77]

3) If the tefillin slipped out of its place, one does not repeat the berachah before returning it to its place. This applies even if the entire shel yad or shel rosh moved from its place, and regardless of whether or not this occurred during the prayer service. Similarly, if the knot of the tefillin shel yad became untied, one does not repeat the berachah before retying the knot.[78]