What material must be used to sew the tefillin, and what is the required number of stitches?

Synopsis

It is a halacha l'Moshe miSinai that tefillin be sewn with sinews from kosher animals. Three stitches per side is the standard; some require all 12 stitches with a single thread. The Rema notes that fewer than 12 stitches (even 10) does not invalidate.

Early Acharonim
Lenient
Strict
Lesser cited
Major authority

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