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Tefillin straps, retzuot, are the number one p'sul, point of invalidation, found when tefillin are checked. Unfortunately most of us do not realize that our tefillin straps need to be examined regularly, in fact much more often than the scrolls and the batim.

There are two aspects of the straps which must be checked:

  • they must have a minimum width
  • they must be black on the outer side

Width of the Retzuot: There are various opinions among the poskim as to the minimum width of kosher tefillin straps. One should always check with his posek, rabbinical authority, to determine which measurement is acceptable for him. Ideally the straps should be at least 11 mm wide. New standard straps average 14 to 15 mm wide. This is so that when they thin out due to stretching in normal use they will still retain the minimum required width. Because of this natural stretching and narrowing the straps must be checked periodically. Tefillin straps can also tear, especially in the area of the knots and those points where they are wrapped around the arm when worn and around the covers when being stored.

Blackness of the Straps: Tefillin straps must be totally black on the outer side. This is a requirement, "Halacha l'Moshe m’Sinai” and not minhag, custom or a segula. Tefillin straps which are not black invalidate the entire mitzvah of tefillin shel yad or tefillin shel rosh.

The blackness of the straps can only be determined when being worn. Cracks and crevasses often can only be seen when the straps are bent, at which time they appear as clearly not black. Cracks can and do occur in both standard straps which are black on one side, as well as the double-sided black straps available today. These cracks can invalidate the straps.

The easiest way to examine your tefillin straps is to look at them when you are wearing them. Carefully check if they are really black on the top and if they are wide enough. If they don't look totally black then you have two options: either paint them with kosher tefillin paint or replace them. If they are not wide enough they must be replaced.

The most common cause of cracked tefillin paint or thinning retuzot is the way you wrap the straps when you put the tefillin away. The leather of the retzuot and the paint used on them do not have the same degree of elasticity. If you stretch the retzuot too much or wrap them very tightly around the covers the result will be that the paint will crack and sometimes actually peel. An easy way to check if you are wrapping your straps too tightly is to look at the underside of the straps as you begin to wrap them around the cover. If the bottom of the strap shows any sign of indentation into the leather you are winding it too tight. The more loosely the strap is wrapped around the cover the longer it will last. As we like to say at HaSOFER: stress free tefillin straps are the beginning of a stress free day.

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