1. The leather for the straps must also be from a ritually pure animal, bird or beast. It’s good if it’s from a calf (Rabbi A. of ?Sond?heim: as for the hair, explained in the preceding chapter), and it must be processed lishmah; if it is not processed lishmah it is invalid, and blacking it lishmah doesn’t change this. They are valid whether made from leather or from klaf.
2. It is halakha from Moses at Sinai that the straps should be black on the outside. One must be exacting and see that they are always as black as possible; if they get scuffed he should blacken them again. It seems to me that one should also blacken the edges – the place where it was cut. If one applied the oil of an impure fish to the leather (dialect word) [gives the paint layer elasticity] it is not a problem, because this oiling is not an integral part of the blackening. It is integral that the black pigment come from a ritually pure source, and oiling it just sharpens the way the paint appears and softens the leather, to make it nice, so one need not worry if it came from a ritually impure source (Noda be-Yehudah tenina, sec.3,4), but it is far better to make sure one uses a kosher oil (see chapter 17:4, about patches which are applied after sewing. Also see 3:3).
3. The blackening must be done lishmah by a sentient Jewish adult; if they were not done lishmah, or done by a non-Jew, they are invalid even bedeavad, even if a Jew re-blackened them lishmah. If one didn’t have any other straps, he should blacken the other side lishmah (Peri Megadim), but lekhatḥilah they should be “their beauty is outwards” [Menaḥot 35b] – it is black and smooth, for the best way of doing the mitzvah (if a woman or a child did the blackening under the supervision of a male, see Excursus 18).
4. The straps for both the shel rosh and shel yad should not be narrower than a barley grain (so say the posekim, and Melekhet ha-Shamayim locates it in the Tanḥuma, at the end of parshat Bo). The left and right straps of the shel rosh should reach to his navel, or a little above; some say that the right one should reach to his circumcision (Shimusha Rabba), and it is proper lekhatḥila to be thus stringent. Lekhatḥila the strap of the shel yad should be long enough to tighten it on his arm, wrap around his arm seven times and reach to his middle finger, wrap three times around the middle finger and tie. If he doesn’t have enough for the seven wraps, only enough to tighten it on his arm and make the three wraps on his middle finger and tie, bedeavad this is sufficient. If one makes either set of straps longer, this is fine.
5. The tefillin knot is halakha from Moses at Sinai. That is, the knot of the shel rosh must look like a dalet. There are those who make it square, and this is not right; it must look like an actual dalet. It is impossible to teach this by writing; you must see it done. That of the shel yad must look like a yud, in order to complete the word “Shaddai” which is started with the shin on the shel rosh. One should not tie the knots until after the shin has been made on the housing of the shel rosh; then he should tie the dalet, and then the yud, as per the order of the letters in the Name. One should make the knots lishmah, and should not have a woman or a child make them (Peri Megadim, and see Excursus 18).