The Yerushalmi is discussing the reason that tefillin are not worn on Shabbos and Yom Tov. The Yerushalmi first cites a derasha: “V’shamarta es ha’chukkah ha’zos me’yamim yamima- v’lo leilos” (this pasuk, in Shemos 13, is in one of the parshiyos of tefillin). Both Prof. Leiberman and R’ Chaim Kanievsky here insert [Yamima – prat l’Shabosos v’Yomim Tovim]. The Gemara subsequently darshens “V’hayu lecha l’os – me she’trichin os, yotz’u Shabbosos v’Yomim Tovim.”
The Gemara then asks – did we not already derive this from Me’yamim Yamima?
The Gemara answers with a fundamental principle from R’ Yochanan: “Kol mila d’lo mechavara mesamchin lei min asrin sagin.” – Anything that is not clear we sustain from many places.
The Nimukei Ysoef at the beginning of Ha’Chovel in Bava Kama explains (in the name of the Ra’ah): Anything that we know to be true, but it is not clear to us what source in the Torah is its basis; permission is granted to anyone to expoound it and bring support from the Scripture. Even though normally a person cannot expound a gezeira shava on his own, unless he received it from his Rebbe, that refers to an entirely new gezeira shava, i.e., in the ayin tachas ayin or shor tachas shor gezeira shavas there in BK, there must be a kabbaala that the din is mammon; once there is such a kabbalah; however, anyone can propose a gezeira shava such as tachas-tachas.
As Prof. Lieberman notes, however, “lo mechavra” in Yerushalmi generally means an asmachta; i.e., the issur on tefillin on Shabbos is not d’orysa mamash. This is also evident from the continuation of the sugya, where the permissibility of wearing the teillin on Shabbos to save them is dicussed in light of whether the issue is mechuvar or not; nevertheless, R’ yochana’s principle itself can have both meanings – something which is not explicit in Torah – whether it is because it is essentially a mesorah, yet neverhteless a d’orysa; or because it is an asmachta – is to be sustained from many places.
Other examples of this abound, such as the Bavli’s discussion of how we know an esrog is the pri eitz hadar of th pasuk, etc.
BTW, there will probably not be a DHM”Y next week, as I am giving several major shiurim next Thurs.-Shabbos.
Those in the vicinity, please join us at our regular Sun. night shiur this week as we continue on the topic of Office Parties and discuss the moshav leitzim aspect. Contact me for more information.