Talmud su Salmi 16:8

First they were giving them¹³⁷The tefillin, when somebody was entering a toilet. In the parallel in the Babli (Berakhot 23a), it is not mentioned that first one had to hand the tefillin, which represent a considerable monetary worth, to other people. to others; these were taking them and fleeing. They decreed that one should put them in holes in the wall. When that incident¹³⁸The incident is decribed in detail in the Babli (loc. cit.): A prostitute found a pair of tefillin in a hole near a public toilet, took them, and bragged publicly that she had received them for her services from a certain holy man who then committed suicide as a consequence of the public scandal. happened, they decreed that a person should enter and keep them in his hand. Rebbi Jacob bar Aḥa¹³⁹A colleague of Rebbi Zeïra. The argument here, relating to a toilet, is parallel to the preceding one, relating to a urinal. in the name of Rebbi Zeïra said: but only if there is time left during the day to put them on again. But if there is no time left in the day to put them on, it is forbidden. For if he cannot perform a mitzwah with them, why should he degrade them? Maisha (Moses), grandson of R. Joshua ben Levi, said: He who wants to do it right, makes for them a pouch the size of a hand-breadth and puts them on his heart¹⁴⁰A pouch with straps so that in case of need one can put the tefillin in the pouch and carry them hanging under his outer garment, the strap going around his neck. Since one needs the pouch anyhow for storing the tefillin during nighttime, the counsel of Rebbi Maishe is only to put the straps on so that the pouch can be used also during daytime. The Babli (24a) forbids expressly to have the tefillin hanging on its own straps (not those of a pouch).. What is the reason? (Ps. 16:8): “I put the Eternal always before me.” There¹⁴¹In Babylonia. The parallel in the Babli (Šabbat 49a) reads: “Rebbi Yannai said: Tefillin need a clean body, like Elisha of the bird’s wings.” R. Z. Frankel points out that at the start of fol. 4c, the Yerushalmi quotes that “Rebbi Yannai said: Tefillin need a clean body”; hence, the reference to Elisha of the bird-wings is really a Babylonian addition. The story is told only in the Babli, loc. cit., that Elisha was wearing tefillin when, in the aftermath of the war of Bar Kokhba, wearing tefillin was a capital crime. But he took them off when he saw a policeman and kept them in his hands. When the policeman asked him what he held in his hands, he said: “a couple of bird’s wings.” When he was ordered to open his hands, two birds flew away and his life was saved. (This story shows again that tefillin cases were not supposed to be larger than about 3/8th of an inch square.)
The implication of this Babylonian ruling is that nobody can be expected to keep his body perfectly clean for very long; hence, tefillin should be removed after prayers. they say: He who is not like Elisha of the bird’s wings should not put on tefillin.