The tefillin straps (retzu’ot)

 The tefillin straps (retzu’ot)

The entire length of the straps must be black. They must be at least 9 mm wide. It is advisable to purchase wider straps because with the passage of time and use, they stretch out and become narrow.
Quotation from tractate Brachot – (use translation in addition to original)

Berachot 6(A)
Rav Avin bar Rav Adda said in the name of R’ Yitzchak: How do we know that the Al-Mighty wears tefillin? For it says, Hashem has sworn by His right hand and by the arm of his strength. “By his right hand”, refers to the Torah, as it states, “From His right hand (he gave) the fiery Torah to them. “And by the arm of his strength”, refers to tefillin, as it says, Hashem will give “strength” to His people, and this alludes to tefillin.
And how do we know that tefillin are the strength of Israel? As it says, “All the nations of the world will recognize that the Name of Hashem is upon you, and they will fear you; and it says further, R’ Eliezer the Great says, that which generates this fear are the Tefillin worn on the head.

 

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