Is It Permitted to Cut Tefillin Straps That Are Too Long?

Greetings,

It is permitted to cut tefillin straps when there is a need to do so. It is good to be careful, when possible, not to cut with iron.

Sources: Regarding the permission to cut tefillin straps, see Responsa Chayei HaLevi, volume 3 (siman 3, letter 3), where he heard from a great authority that the custom of the world is to be lenient in this matter. See there his view on this.

We find regarding tzitzit that one should not cut them with a knife (Magen Avraham, siman 11, s.k. 18, בשם the Shlah and the Matteh Moshe, and brought in Mishnah Berurah, s.k. 61). This is not a prohibition, only that it is good to be careful, as the Shulchan Aruch HaRav writes there, section 24.

The reason for being careful, as the Shulchan Aruch HaRav writes there, is along the lines of the verse, You shall not wield iron over them, etc. So too wrote the Machatzit HaShekel (s.k. 18). The meaning is that since there is a segulah in the mitzvah of tzitzit to lengthen life (see tractate Shabbat 32b, where one opinion states that for the sin involving tzitzit, children die), therefore one should not wield iron over it, like the altar concerning which it is said (Devarim 27:5), You shall not wield iron over them. The reason, as written in tractate Middot (chapter 3, mishnah 4), is that iron was created to shorten a person's life, while the altar was created to lengthen a person's life, and it is not fitting for that which shortens to be wielded over that which lengthens. According to this, it seems that there is reason to be careful also with tefillin, for the Sages said in tractate Menachot (44a-b), Whoever dons tefillin lengthens his days, as it is said (Yeshayahu 38:16), The Lord, through them, shall let them live. Thus, the same reason applies, that that which shortens should not be wielded over that which lengthens.

With blessings,

Hillel Meirs