[41a - 24 lines; 41b - 6 lines]
1)[line 5]יבא עשה וידחה את לא תעשהYAVO ASEH V'YIDCHEH ES LO SA'ASEH
(a)When an Isur Lo Sa'aseh prohibits a certain action that prevents a person from performing a Mitzvas Aseh, the Torah states that the Aseh is able to "push aside" the Lo Sa'aseh. For example, when a person wants to wear a four-cornered linen garment, the Isur of Sha'atnez prohibits attaching woolen threads to it. However, the Mitzvah of Tzitzis requires adding threads of Techeles (that are made of wool) to this garment. The Torah commands that in this case the Mitzvas Aseh overrides the Lo Sa'aseh.
(b)The Tana'im argue as to the source of this Halachah. Some learn it from the fact that the Torah specifically wrote the Mitzvah of Tzitzis and the Isur of Sha'atnez as adjacent verses (Semuchin), an indication that the Mitzvah of Tzitzis overrides the Isur of Sha'atnez (Yevamos 4a). Others learn it from different sources (Yevamos 5a, Nazir 41a, 58a).
(c)Even though an Aseh normally overrides a Lo Sa'aseh, this is not the rule in every case. The Gemara explains that in certain instances, the Aseh does not have the power to override the Lo Sa'aseh. Some examples are:
1.A Lo Sa'aseh that is punishable by Kares is not pushed aside by an Aseh (Yevamos 3b).
2.An action that is prohibited by both a Lo Sa'aseh and an Aseh, is not pushed aside by a different Mitzvas Aseh (Chulin 141a).
3.Only in a case where the performance of the Aseh coincides with the transgression of the Lo Sa'aseh did the Torah command that the Aseh takes precedence. If performance of the Aseh is only accomplished after the transgression of the Lo Sa'aseh, the Lo Sa'aseh is not pushed aside (Shabbos 133a). (There are those who write that if a person begins to perform a Mitzvas Aseh while transgressing a Lo Sa'aseh, even though the Aseh is not yet completed by the time the Lo Sa'aseh is transgressed, it pushes aside the Lo Sa'aseh - NIMUKEI YOSEF to Bava Metzia 33a.)
4.If it is possible to perform the Aseh, in the case under discussion, without transgressing the Lo Sa'aseh (by performing the Aseh in a different way or at a different time), the Aseh does not push aside the Lo Sa'aseh (Yevamos 20b - see TOSFOS YESHANIM to Shabbos 25a). (The Rishonim argue as to whether an Aseh pushes aside a Lo Sa'aseh when it is possible to perform the Aseh without transgressing the Lo Sa'aseh, through the use of a certain item that the person does not currently have the means to obtain (RASHBA to Yevamos 4b).)
(d)The Rishonim explored the possibility that an Aseh also does not push aside a Lo Sa'aseh in other cases:
1.When one person performs a Mitzvas Aseh by doing a certain action in which two people transgress the Lo Sa'aseh.
2.When the action is prohibited by two Mitzvos Lo Sa'aseh, and not only one (TOSFOS to Yevamos 3b DH Lo Sa'aseh).
3.When the action is prohibited in another instance by a Lo Sa'aseh and an Aseh, even though in the case at hand there is only a Lo Sa'aseh that prevents it (TOSFOS to Kidushin 34a DH Ma'akeh).
2)[line 6]"[והיה ביום השביעי יגלח את כל שערו את ראשו ואת] זקנו [ואת גבת עיניו ואת כל שערו יגלח...]""[V'HAYAH VA'YOM HA'SHEVI'I YEGALACH ES KOL SE'ARO; ES ROSHO, V'ES] ZEKANO, [V'ES GABOS EINAV, V'ES KOL SE'ARO YEGALE'ACH...]"- "[And on the seventh day he shall shave off all of his hair; [the hair of] his head], his beard [and his eyebrows and all of his hair he shall shave off. And he shall immerse his clothes, and immerse his flesh in water, and he shall be Tahor.]" (Vayikra 14:9)
4)[last line]מגדיליםGEDILIM- twisted threads, i.e. Tzitzis
5a)[last line]"לא תלבש שעטנז [צמר ופשתים יחדו. גדלים תעשה לך על ארבע כנפות כסותך אשר תכסה בה]""LO SILBASH SHA'ATNEZ; [TZEMER U'FISHTIM YACHDAV. GEDILIM TA'ASEH LACH; AL ARBA KANFOS KESUSCHA ASHER TECHASEH BAH.]"- "You shall not wear Sha'atnez (combined fibers); [wool and linen together. You shall make for yourselves twisted threads (Tzitzis); on the four corners of your garment with which you cover yourself.]" (Devarim 22:11-12)
(a)Sha'atnez is a mixture of wool and linen which is prohibited, as the Torah states in Devarim 22:11. Chazal teach that the word "Sha'atnez" is made up of three smaller words - "Shu'a" (combed), "Tavi" (spun), and "Noz."
(b)The Rishonim disagree over the translation of the word "Noz":
1.RASHI (Nidah 61b and Horayos 11a DH Noz) and the RASH (Mishnayos Kil'ayim 9:8) learn that Noz means woven together (the wool and linen are woven together in a garment).
2.TOSFOS (Nidah 61b DH Shua Tavi v'Noz) disagrees with Rashi's explanation. We learn that the prohibition of Sha'atnez applies only when the wool and linen are woven together from the word "Yachdav" in the verse. If so, Noz does not mean "woven together." Rather, Noz means that the threads must be twisted or wound.
(c)The Rishonim disagree about how the wool and linen must be joined in order to transgress the Torah prohibition of Kil'ayim:
1.RASHI (ibid.) holds that the wool and linen must be combed, spun, and woven together. That is, the strands of wool must be combed together, spun together, and then woven together with the linen in order to transgress the prohibition of Sha'atnez. If the strands of wool are combed or spun separately from the strands of linen, even though they are later woven into a garment together, the Torah prohibition of Sha'atnez has not been transgressed.
2.TOSFOS (ibid.) learns that one transgresses the Torah prohibition if the wool and linen are combed, spun, and twisted by themselves, and are then joined together by two stitches. The RASH (ibid.) agrees with Tosfos, and rules that if the wool and linen are combed and spun separately and then joined, the prohibition of Sha'atnez has been transgressed. (However he does not require that the threads be twisted, see b:1.)