Mishneh Torah (Rambam) משנה תורה

There are eight requirements in the making of tefillin. All of them are halachot transmitted to Moses on Mount Sinai and, therefore, it is necessary to fulfill them all. If one deviates with regard to any of them, the [tefillin] are unacceptable. They are: a) The tefillin must be square and must be sewn closed in a square. [Both] diagonals must be equal, and thus all four angles will be equal. b) The leather of the head [tefillin] should have a shin embossed on both its right and left sides. c) The passages should be wrapped in fabric. d) A hair should be wound around that fabric. Afterwards, they should be placed in their compartment. e) They should be sewn [closed] with the sinews [of an animal]. f) The leather compartment in which they are placed should have a place for the straps to pass through so that they can be moved through the [tefillin's] handle. g) The straps should be black. h) The knot with which they are tied should be the renowned knot that is formed like a dalet.

How are the head tefillin made? We take a cubic wooden block. [It need not, however, be a perfect cube]. If its height is [slightly] more or less than its width, it is of no consequence. We are required to take care only that its width and length are alike. Three grooves are carved into it so that four projections will be made as depicted. Leather is taken and soaked in water, and then, the mold is placed within it. The leather is inserted in between the grooves. While [the leather] is still wet, it is plucked and squeezed until the shape of a shin with three heads is formed on the right side of the tefillin as they will be worn, and the shape of a shin with four heads is formed on the left side of the tefillin as they will be worn.

The leather is then left on the mold until it dries, and then it is removed. Thus, the leather will be [formed into a block] with four empty compartments. One of the passages from the Torah is placed in each compartment, and then a portion of the leather is folded over beneath them, and then they are sewn closed on all four corners. Within this lower piece of leather, a place should be left for the straps to be inserted, like a handle. It is called a ma'aboret.

How are the tefillin of the arm made? We take a wooden block whose length is equal to its width and is a fingerbreadth - or slightly more or slightly less - high, and place wet leather around it. The leather is left on this mold until it has dried, and then it is removed. The four passages are deposited in the place left by the mold. A portion of the leather is folded over beneath them, and then they are sewn closed on all four corners. A piece of leather, like a handle, should be left for the straps [to be inserted].

What is the order of the passages? For the head tefillah, the final passage, V'hayah im shamo'a, is placed in the first compartment on the right side of the person putting on the tefillin. Shema is placed next to it. V'hayah ki y'viacha is placed in the third compartment next to Shema, and Kadesh Li is placed in the fourth compartment, on the left side of the person putting on the tefillin. Thus, a person who is facing the person wearing the tefillin will read them in the following order. If their order is altered, they are not acceptable.

[The passages for] the arm tefillin are written on four columns on a single piece of parchment like a Torah scroll, according to the order in which these passages are found in the Torah, in the following manner: If they were written on four separate pieces of parchment and placed in the same compartment, one fulfills one's obligation. There is no need to glue them together.

When the passages - both of the head and the arm tefillin - are rolled closed, they should be rolled from the end to the beginning, so that were the passage to be rolled open, it would be possible to read each portion from the beginning to the end.

Before the passages are placed in their compartments, they should be wrapped in a fabric, and hair should be wound around them. Afterwards, they may be placed in their compartments. This hair should be from a kosher species of animal or beast. Even when these animals died without being ritually slaughtered or were treifah, [their hair is nevertheless acceptable]. It has already become a universally accepted custom to wind hair from the tail of a calf [around these parchments].

When the tefillin are sewn closed, they may be sewn only with sinews from a kosher species of animal or beast. [Sinews taken from] animals which died without being ritually slaughtered or which were treifah [are nevertheless acceptable]. It is customary to take sinews from the heels of kosher animals and beasts. They are white in color. If they are too firm, they are softened by [pounding them with] stones and the like until they become like flax. Afterwards, they are spun and twisted into threads and used to sew together tefillin and the sheets of Torah scrolls.

When the tefillin are sewn closed, they should be sewn as a square. It is a widely accepted practice for there to be three stitches on each side, so that there will be twelve stitches in all. This applies for both the arm tefillin and the head tefillin. If, however, one made ten or fourteen stitches, there is no difficulty. For each of the stitches, the thread must pass through from both sides.

The groove between [each of the compartments] of the head tefillin should reach the stitches [which sew the tefillin closed]. [Nevertheless,] if the groove is discernible, so that the [division into] four compartments is openly visible, [the tefillin] are acceptable even if the groove does not extend until the stitches. If, however, the groove is not discernible, [the tefillin] are not acceptable. It is necessary to pass a thread or cord through each of the grooves on [the outer side of] the leather [compartments] to separate between the compartments. It is common custom to pass one of the sinews used to sew [the tefillin closed] between each of these three grooves.

How are the straps made? We take leather straps [at least] the length of a barley-corn in width. If they are wider than that, they are acceptable. The length of the straps of the head tefillin should be sufficient to surround the head, tie the knot, and extend on either side of the head until they reach the navel or slightly above it. The length of the strap of the arm should be sufficient to surround the forearm, tie its knot, and extend until it can be wound three times around the middle finger and tied. If the straps are longer than this, they are acceptable.

One places the straps through their handle, leaving space for the [circumference of] one's head, and ties a square knot, which resembles a dalet. Every Torah scholar should learn how to tie this knot. It is impossible to describe this knot in writing. Rather, it must be seen. The straps of the hand tefillin should be tied with a knot that resembles a yud. This knot should allow the strap to pass through it so that it can be widened or narrowed while one is tying the tefillin on one's arm.

The outer surface of the straps of both the head and the arm tefillin must be black. This is a halachah transmitted to Moses on Mount Sinai. In contrast, with regard to the inner surface, since it faces the inside, it is acceptable if it is green or white. One should not make this [side of the straps] red, since it will be embarrassing for him if they become overturned. The back of the straps should be the same color as the compartment; if it is green, they should be green; if it is white, they should be white. It is attractive for tefillin to be entirely black, the compartments and the entire strap.

The leather used to cover the tefillin and from which the straps are made should come from a kosher species of animal, beast, or fowl. Even when these animals died without being ritually slaughtered or were treifah, [their hides are nevertheless acceptable]. If, however, leather from a non-kosher species was used or if they were covered with gold, they are not acceptable. The leather used for the straps must be processed with the intent that it be used for the mitzvah. In contrast, the leather used to cover the tefillin need not be processed at all. It is even acceptable if it is made from matzah. [Indeed,] this is the practice in many communities.

tefillin may be made only by a Jew, since making them is equivalent to writing [the passages], because of the shin [embossed] in the leather [compartment] mentioned above. Therefore, if they were made by a gentile or sewn closed by him, they are unacceptable. Similarly, they may not be made by any others whose writing [of the passages] is not acceptable.

A head tefillah may not be made into an arm tefillah, but an arm tefillah may be made into a head tefillah, because an article should not be lowered from a higher level of holiness to a lesser one. Similarly, the strap of a head tefillah should not be used for an arm tefillah. When does the above apply? After one has worn them. However, if head tefillin have never been worn, one may make them into arm tefillin. How is this done? One drapes leather around them until they become a single [compartment] and [then, one can] tie them on his hand.

[The following laws apply when] the stitches of the tefillin become torn: If two stitches which are located next to each other become torn, or three stitches become torn even though they are not located next to each other, [the tefillin] are unacceptable. When does the above apply? With regard to old [tefillin]. With regard to new [tefillin], however, if their base remains intact, they are acceptable. [tefillin are considered] to be "new" as long as the leather remains strong and does not tear when one takes hold of a portion of the leather where the stitch was torn and hangs the tefillin. If the leather is not fit to hang the tefillin because it will tear, the [tefillin are considered] "old."

Should a strap be torn, [the pieces] should not be tied or sewn together. Rather, it should be removed and entombed, and another one [substituted for it]. The remnants of [torn] straps are not acceptable unless their length and width meets - or exceeds - the minimum requirements. At all times, a person should be careful that the external surface of the straps faces upward when he ties them on his arm and head.