Tefillin, also known as phylacteries, are leather objects used in Jewish prayer, containing Biblical verses. They are a vital part of morning prayer services, and are worn on a every day basis (except Sabbath and festivals) by lots Jews.
The origin of wearing tefillin comes from the Torah (five books of Moses), in Deuteronomy 6:8, 11:18; Exodus 13:9, 16. While these passages were interpreted directly by most commentators (compare, though, the view of the Karaites, Abraham ibn Ezra, and Rashbam on Exodus 13:9), the Rabbis held that the general law only was expressed in the Bible, the application and elaboration of it being directly matters of the oral law. The previously tannaim (rabbis of the Mishnah) explicated their views of the tefillin in the Mishnah and Talmud. (Talmud references: Menachot 34b; Zeb. 37b; Sanhedrin 4b; Rashi and Tosafot ad loc. )Tefillin incorporates two leather boxes, one worn on the arm and known as “shel yad”, and the other worn on the head and known as “shel rosh”. They are produced of the skins of kosher animals.
According to traditional Jewish law, the boxes must be square; their height should be about the length or the width; and they should be dyed black. The boxes are fastened on the under side with square pieces of thick leather by twelve stitches, and are provided with loops at the ends, by ways of which are passed leathern straps. They are blackened on the outside. The threads are elaborated from the veins of kosher animals.
The strap that is passed by ways of the head-tefillin ends at the back of the head in a knot representing the letter ?; the one that is passed by ways of the hand-tefillin is educated into a noose near the box and fastened in a knot in the shape of the letter ?. The box containing the head-tefillin has on the outside the letter ?, both to the right (with 3 strokes: ?) and to the left; and this, in association with the letters educated by the knots of the two straps, make up the letters of the Hebrew word Shaddai (“Almighty”), one of the names of God.
The measurements of the boxes aren’t given; but it is adviced that they shouldn’t be smaller than the width of two fingers. The width of the straps should be equal to the length of a grain of oats. The strap that is passed by ways of the head-tefillin should be long enough to encircle the head and to enable for the knot. The two ends, falling in front through either shoulder, should reach the navel, or somewhat above it. The strap that is passed by ways of the hand-tefillin should be long enough to enable for the knot, to encircle the whole length of the arm, and then to be wound 3 times around the middle finger.
