My son had put on the Shel Yad.
I was showing him how to take the Shel Rosh out of it’s case and he whispered “I know how.”
Is this considered a hefsek between Shel Yad & Shel Rosh or is it considered for the need of the mitzvah.
Answer:
This is an interesting question.
It appears that because the speech is related to the matter of putting on the tefillin, it will not be considered a hefsek.
See Shulchan Aruch 25:10.
Best wishes and mazal tov for the bar-mitzvah!