Mitzvot Tzrichot Kavana - Minchat Shlomo O.C. 1

 In this teshuva, Rav Shlomo Zalman Auerbach deals with the question of whether or not doing a mitzva without kavana invalidates the performance of that mitzva.  Specifically, he wonders whether someone who eats in a succah but lacks kavana for the mitzva is considered to have eaten outside of the succah, or if someone who wears tzitzit without having kavana for the mitzva is considered as if he failed to wait tzitzit on that garment.  Along the way, he raises further possible ramifications, such as whether one would violate the prohibition of kilayim if he wore wool tzitzit on a linen garment (which is normally permitted for the mitzva) without having kavana to fulfill the mitzva.  After analyzing the question through the perspective of other mitzvot, such as affixing a mezuza to one's door, slaughtering an animal, and putting a fence around one's roof, Rav Auerbach concludes that while one who wears tzitzit without having kavana for the mitzva does not fulfill the mitzva, he also does not violate a lo ta'aseh, where one who sits in a succah with having kavana for the mitzva may be in violation of something since there is the additional requirement of teishvu k'ein taduru.

In the second section of this teshuva, Rav Auerbach determines that if one loses kavana during a mitzva he can still fulfill the mitzva.  His main focus is on someone who is saying Shema or Shemoneh Esrei and his mind wanders.  While he wants to say that it does not count, based on the halacha that someone who is not sure which u'chtavtam he is up to can continue with Shema if he instinctively says l'ma'an yirbu (since we assume that that is where he was up to), he infers that it counts at least b'diavad.  However, if someone is listening to someone else make a bracha or say a tefilla, he can only fulfill his obligation if he listens to the entire thing.

Tzitzit check - Meishiv Davar 1:2

In this teshuva written to the Chafetz Chaim, the Netziv takes issue with a psak written in the Mishna Berura (which was written by the Chafetz Chaim) where he writes that if one has a tallit which is pasul for some reason or another then he may not go outside on Shabbat with that tallit (in a place with no eiruv), and if he does he will be in violation of the prohibition of carrying on Shabbat (presumably he is considered to be carrying the strings).

The Netziv notes that the view of the Mishna Berura is against the overwhelming majority of Rishonim and Acharonim. According to Rashi, if one had techeilet that was not fit for the mitzva then he would violate the prohibition of carrying, but if one only has white strings they are not considered to be that important and thus there is no prohibition (remember, the Netziv lived before the revival of techeilet). According to Tosafot, there would only be a violation if one had a garment with three tzitzit made already and the fourth was missing.

The Netziv does point out that Rav Akiva Eiger leaves open the possibility that one could violate Shabbat with any form of psul in his tzitzit, but the Netziv counters that other than that possibility, there does not seem to be any major support for the position of the Mishna Berura. There also seems to be a view in the Rishonim that tzitzit should not be worn at all on Shabbat for this reason, but the Rosh rejects this as an unnecessary stringency.

Shatnez and Tzitzit - Meishiv Davar 1:1

In this first teshuva in this collection, the Netziv deals with a statement of the Magen Avraham who writes that one can put wool tzitzit on a linen tallit (in seeming violation of the laws of shatnez) if the corners of the tallit have leather patches on them. He initially raises two questions on this position. First, whether or not leather serves as a barrier vis-a-vis the laws of shatnez is actually a debate in the mishna in Kilayim. Second, there is a view that the tzitzit have to be made out of the same material as the corner from which they hang, and if that corner is made out of leather then there would be no obligation to have tzitzit there in the first place.

The Netziv then adduces a gemara in Yevamot which proves from a pasuk that shatnez is not a problem when it comes to tzitzit. However, he responds that the pasuk should not be needed if the leather patch can serve as an effective barrier. In other words, which is the true reason why this set-up should be permitted?

The Netziv spends some time on whether having or not having techeilet makes a difference (he says it does not), and whether this would be considered to be a situation of מצוה הבאה בעבירה. In the end, he concludes that there is no need to make a decree restricting one from making such a tallit, since if someone takes the time and effort to add the leather patches the chances are that we no longer have to worry about shatnez in that case.