Moed Katan, Chapter Three, Mishnah Four
Most of this mishnah continues to deal with writing on the festival.
1) They may not write loan documents during the festival; but if he [the creditor] does not trust him or he does not have food to eat, he may write.
2) They may not write [Torah] scrolls, tefillin and mezuzot during the festival, nor may they correct [even] a single letter, even in the [ancient] Temple-scroll.
3) Rabbi Judah says: a man may write tefillin and mezuzot for himself.
4) And one may spin on his thigh the blue-wool for his fringe.
Section one: Loan documents may not be written during the festival, because one can lend money without a document, using witnesses to secure the loan. The mishnah immediately lists two major exceptions. If the creditor does not trust the borrower enough to lend him money without a document, then they may write a document. The rabbis considered it important enough for the borrower to be able to secure the loan that they allowed the document to be written during the festival. The second exception is interpreted in two different ways. The Jerusalem Talmud interprets it to refer to the borrowerif the borrower needs a loan so that he can afford to eat, the document can be written. The problem with this interpretation is that if the lender trusts the borrower, then he doesnt need a document, and if he doesnt trust him, then the mishnah has already stated that he may write the document. Due to these difficulties, the Babylonian Talmud interprets the clause to refer to the scribe. If he needs his wages in order to eat during the festival, they may have him write the document.
Section two: We might have thought that since Torah scrolls, tefillin and mezuzot are sacred objects, a scribe could write them during the festival. The mishnah rules otherwiseeven holy objects cannot be written on the festival. One cannot even fix one letter in a scroll, even in the ancient Temple scroll, the scroll which was kept in the Temple from which other scrolls were copied.
Section three: Rabbi Judah allows one to write a personal set of tefillin or a mezuzah for personal use, but he agrees with the previous opinion that a scribe may not write these documents in order to sell them. The problem, according to Rabbi Judah, is not inherent in the writing itself. The problem with writing is when it becomes a craft done by a professional.
Section four: The mishnah allows one to spin tzitzit (fringes on the corner of ones garment) but only for personal usage, while the garment is resting on ones thigh. He may not put the threads onto a spinning wheel to spin the tzitzit, the way this is normally done. Again, in order to distinguish something from the way it is done normally, the rabbis demanded it be done differently on the festival.