1 678
     .    .             .  .

Hilchos Tefillin 33 (page 116)
מתחילת סימן לד עד אמצע סעיף ב ויכוון בהנחתם

The Order of the Parshios According to Rashi and Rabbeinu Tam
Wearing Rabbeinu Tam Tefillin
Wearing Both Types of Tefillin at Once

The order of the parshios according to Rashi and Rabbeinu Tam
How are the parshios arranged in the tefillin? According to Rashi and the Rambam, the order from the viewer's right is Kadesh, V'haya ki yeviacha, Shema and V'haya im shemoa. According to Rabbeinu Tam, the order is Kadesh, V'haya ki yeviacha, V'haya im shemoa and Shema. There is an opinion that organizes the parshios from the wearer's right, but this opinion is not cited by the poskim.
( סעיף א, וס"ק ג; ביאורים ומוספים דרשו, 1)
Wearing Rabbeinu Tam tefillin
Many Rishonim side with Rashi; many others side with Rabbeinu Tam. Many Acharonim-- including the Beis Yosef and the Gra-- pasken like Rashi, and this is the longstanding popular custom. There is an opinion cited in Shulchan Aruch and the Arizal which encourages scrupulous people to wear both types of tefillin together. There is a second opinion, also quoted in Shulchan Aruch, which holds that Rashi tefillin should be donned first and Rabbeinu Tam afterwards, and this is the more popular way of wearing Rabbeinu Tam tefillin. It is proper for the Rabbeinu Tam tefillin to be smaller than the Rashi tefillin in order to prevent confusion.
( סעיף א וס"ק ד ו־ה; וראה ביאורים ומוספים דרשו, 8)

Wearing both types of tefillin at once
According to the Arizal, both tefillin should be worn together. The Rashi tefillin are placed on the upper part of the muscle towards the shoulder, and the Rabbeinu Tam tefillin are placed below, towards the elbow. The Rashi shel rosh should be lower on the forehead and the Rabbeinu Tam should be placed above it. The retzuos are wrapped with Rashi on the top and Rabbeinu Tam below, and it is not considered a chatzitza. In order that both tefillin should be donned soon after the beracha, they should be tightened simultaneously.
( ס"ק ה-ו; ביאורים ומוספים דרשו, 7)

  • The Torah's use of the word uk'shartam-which can be read as the phrase uk'shar tam-is understood by Chazal to indicate that the length of retzua that meets the requirement for tefillin should be arranged properly. Many poskim understand this to mean that there should be only one knot on that area of the retzua. Other poskim explain that the phrase mandates that the retzua be complete and untorn.
  • The poskim debate whether a torn retzua can be sewn from below in a manner that the stitches are not visible from the top.

  • Circumstances for violating ba'al tosif

  • Is intention required for ba'al tosif?

  • When is fulfilling the opinions of Rashi and Rabbeinu Tam in violation of ba'al tosif?