only [if he put] a portion that should be inside outside or what should be outside inside, but if he put what should be inside also inside or what should be outside also outside, it does not matter. Thereupon Raba said to him, Why is it that [the placing of] an inside portion outside or of an outside portion inside is not valid? It is, is it not, because that which should look out into the open does not do so, whilst that which should not look out into the open actually does so? Then, likewise, [the placing of] an outside portion also outside or an inside portion also inside [should also be invalid], since what should look out into the open on the right looks out on the left, and what should look out into the open on the left looks out on the right? We must rather say that there Is no such distinction. R. Hananel also said in the name of Rab, The underside of the tefillin is a law given to Moses at Sinai. Abaye said, The duct of the tefillin is also a law given to Moses at Sinai. Abaye also said, The shin of the tefillin is a law given to Moses at Sinai. The division [between the compartments] must reach as far as the stitches. But R. Dimi of Nehardea said, As long as it is noticeable it need not [reach as far as the stitches]. Abaye also said, The parchment [for the Scriptural portions] of the tefillin must be examined against a flaw, since we require the writing to be perfect and it would not be so [if it had a flaw]. But R. Dimi of Nehardea said, This is not necessary, for the pen would detect [any flaw]. R. Isaac said, That the straps [of the tefillin] must be black is a law given to Moses at Sinai. An objection was raised: The tefillin must be tied with straps of the same [material as the tefillin themselves.] The straps may be either green or black or white; but they should not be red because it is repellent, and also for another reason. R. Judah said, It is related of one of R. Akiba's disciples that he used to tie his tefillin with strips of blue wool, and R. Akiba made no comment. But is it possible that that righteous man actually saw his disciple do so and he did not prevent him? They said to him, He certainly did not see him do so, for had he seen him he would not have allowed him. It is related further of Hyrkanos the son of R. Eliezer b. Hyrkanos that he used to tie his tefillin with strips of purple wool, and he [R. Eliezer] made no comment. But is it possible that that righteous man actually saw his son do so and he did not prevent him? They said to him, He certainly did not see him do so, for had he seen him he would not have allowed him. Now it is stated here, at all events, [that the straps may be] either green or black or white! — This is no contradiction, for here it speaks of the outside of the strap and there of the inside. But if of the inside, how can it be repellent or give any ground for suspicion? — It might sometimes become twisted. A Tanna taught: That the tefillin must be square is a law given to Moses at Sinai. R. Papa said, [This refers to] the stitching and the diagonal. Shall we say that the following [Mishnah] supports this view? For we have learnt: If a man made his tefillin round, it is a danger and it is no fulfilment of the precept! — R. papa said, That [Mishnah] deals with the case where they were made round like a nut. R. Huna said, As long as the surface of the sides of the tefillin is whole they are valid. R. Hisda said, If two [sides] were split they are still valid; but if three, they are invalid. Said to him Raba, Your ruling that if two [sides] were split they are still valid is true only if [the rents were] not facing each other, but if they were facing each other they are invalid. And even if they were facing each other [they are invalid] only if they were new [tefillin], but if they were old it would not matter. Abaye asked R. Joseph, What is meant by new, and what by old? He replied, If when one stretches the leather it rebounds, it is old; otherwise it is new.ᵃᵇᶜᵈᵉᶠᵍʰⁱʲᵏˡᵐⁿᵒᵖᵠʳˢᵗᵘᵛ