To Purchase this Sefer 
The Torah commands every male Jew to tie fringes onto the corners of four cornered garments that he wears. It is forbidden to wear any garment that is obligated in Tzitzis and does not have Kosher Tzitzis placed on all of its four corners. One who wears such a garment transgresses a positive command, as he has nullified the Mitzvah of Tzitzis. [The Gemara states that one who does so transgresses five positive commands.] See chapter 3 for the full details of which garments are obligated in Tzitzis, and the conditions required for Kosher Tzitzis strings.
How many Mitzvos are fulfilled by wearing Tzitzis? One who wears a four cornered garment with Tzitzis on each corner fulfills a single Biblical positive command.
May one wear a four cornered garment without Tzitzis if he is already wearing a pair of Tzitzis? All four cornered garments are obligated to have Tzitzis attached to their corners even if one plans to wear a number of them at the same time, and one of these garments already contains Tzitzis. [Thus, even one who is wearing a Tallis Katan remains prohibited from wearing another four cornered garment that does not contain Tzitzis.]
May one wear more than one pair of Tallis Katan at a time? It is permitted to wear more than one Tallis at a time, whether one wears a Tallis Gadol and Tallis Katan at the same time, or wears two or more pairs of Tallis Katan. There is no prohibition at all involved in doing so.
Do four cornered garments require Tzitzis if one does not plan to wear it? Four cornered garments are only obligated to have Tzitzis attached to their corners while they are being worn. It is thus permitted to own four cornered garments that do not have Tzitzis, so long as one does not wear them. It is for this reason that a blessing is not recited when tying Tzitzis onto a four cornered garment which one desires to wear, as the Mitzvah is not completed with the attachment of the Tzitzis, but rather at the time of wearing it.
The Mitzvah of Techeiles: See Chapter 4 Halacha 4!
When were the Jewish people commanded the Mitzvah of Tzitzis?
The Jewish people were commanded the Mitzvah of Tzitzis after the incident of “Mikosheish Eitzim” occurred on Shabbos. After this incident, Moshe said to Hashem “During the week they have Tefillin which they wear to remind them of the Mitzvos; on Shabbos however, when Tefillin is not worn, what will remind them of the Mitzvos?” Hashem replied “I am giving you the Mitzvah of Tzitzis through which you will remember [the commands]”. This is why the Parsha of Tzitzis begins with “Vayomer Hashem El Moshe” and not the standard wording of “Vayidaber Hashem El Moshe”, as Vayomer implies that Hashem is answering a request that was made by Moshe.
Does one perform a Mitzvah at every moment that he wears Tzitzis, or only at the initial wearing?
Is there a Mitzvah to look at the Tzitzis?
Some Rishonim rule that aside for the positive command to wear a four cornered garment with Tzitzis, there is an additional positive command, which counts as another one of the 613 Mitzvos, to look at the Tzitzis. In their opinion, the Mitzvah is to look at the Tzitzis and hence remember Hashem’s Mitzvos. The Arizal writes that one is required to look at his Tzitzis at every moment. There are also many Segulos associated with looking at the Tzitzis, as will be explained in Halacha 3. For this reason many Torah leaders and Tzaddikim were accustomed to look at their Tzitzis at every opportunity. There is also a tradition amongst meticulous Jews that if they are sitting idle, they touch the Tzitzis and look at them. Based on this, whenever one looks at his Tzitzis he should have in mind to fulfill the positive Mitzvah of “Ureisem Oso”.
Q&A on wearing four cornered garments without Tzitzis
May one wear a four cornered garment without Kosher Tzitzis if there are no Kosher Tzitzis strings available?
Some Poskim rule that if there are no Kosher Tzitzis strings available in the city, there is no Biblical prohibition involved in wearing a four cornered garment without Tzitzis. Nevertheless, even according to their opinion, it is Rabbinically forbidden to do so. Other Poskim however rule it is Biblically forbidden to wear a four cornered garment even in such a case. The practical ramification is regarding a case that one found an invalidation on the Tallis that he is wearing and he is embarrassed to remove it, as will be explained in Chapter 4 Halacha 15.
May one wear a four cornered garment without Tzitzis if his intent is not for the sake of wearing it as clothing?
Yes. One may therefore try on a Tallis Katan/Gadol to see if it is the right size, or to show someone how it is worn. See Chapter 3 Halacha 9C for the full details of this matter.
 8/28; Michaber 8/17
 Parshas Shelach 15/38; Ki Seitzei verse 12
 13/1; Michaber 13/1; Mishneh Menachos 28a; See P”M 13 M”Z 5 that this applies even according to Rebbe Yishmael who holds each corner is a separate positive command
The reason: All four corners of Tzitzis are considered a single Mitzvah, and therefore so long as a Tallis does not have all four Tzitzis attached to it, it is not Kosher. [ibid]
 Menachos 44a
 As the Torah states the command of wearing Tzitzis on five different occasions; 1) Veasu Lahem Tzitzis; 2) Venasnu Pesil Techeiles; 3) Vehaya Lachem Letzitzis; 4) Ureisem Oso Uzechartem; 5) Gedilim Taaseh Lecha. [Rashi ibid]
 13/1; Michaber 13/1; Mishneh Menachos 28a
The reason: As all four corners of Tzitzis are considered a single Mitzvah. [ibid]
Other opinions: Rebbe Yishmael in Mishneh Menachos 28a is of the opinion that each of the four corners is a separate Mitzvah, and one hence fulfills four positive commands in wearing Tzitzis. We rule like Chochamim.
 8/21; Michaber 8/12
Other opinions: Some Poskim rule that only the most upper four cornered garment that is worn is obligated in Tzitzis. [Orchos Chaim brought in Beis Yosef 8] Practically we do not rule like this opinion
 The reason: This is learned from the verse “Al Kanfei Bigdeihem” which is said in plural and hence implies that every four cornered garment that one wears has an individual Tzitzis obligation, irrelevant to how many pairs one is wearing. [Admur ibid; Levush 8/12] The novelty of this ruling is that we do not say that since one is already wearing one pair of Tzitzis, and has hence fulfilled the purpose of the Mitzvah which is to have a constant reminder of the Mitzvos near him, he therefore is exempt from placing Tzitzis upon subsequent four cornered garments that are worn simultaneously, and rather they are all individually obligated
 8/21; Michaber 8/12
Other Opinions: Some Poskim rule that one is not to wear more than one pair of Kosher Tzitzis at a time. [Ralbag end of Shelach] Practically we do not rule like this opinion. [Toras Chaim Sofer 24/3]
 Although it is not the widespread custom even amongst Tzaddikim to specifically wear more than one Tallis Katan, nevertheless if one desires to do so there is no prohibition involved. It is recorded that several Torah sages were accustomed to wear more than one Tallis Katan in order to fulfill their obligation of Tzitzis according to all opinions.
 Thus, one who does not desire to remain even one moment without a Tallis Katan upon changing the Tallis to another pair, he can first put on the new pair and then remove the old pair. Likewise, if one is cold and desires to wear a few pairs of wool Tallis Katan’s to keep him warm, or one is traveling and desires to wear a few pairs to prevent overweight luggage, one may do so without worry.
 Admur 19/1; Michaber 19/1 as rules the Rambam, Rif, Rosh, as brought in Beis Yosef 19
Other opinions: Shmuel of the Gemara is of the opinion that all four cornered garments that one wears are obligated in Tzitzis even when one is not wearing them, and they are rather folded in ones closet. [Menachos 41a] Some Poskim rule like this opinion. [Bahag brought in Beis Yosef 19; Raavan brought in Hagahos Maimanis 3/3 and P”M 19 M”Z 1; Baal Haittur] Practically, although we do not rule like this opinion, being that the three major Rishonim [Rambam, Rosh, Rif] argue against it [Beis Yosef 19] nevertheless some are stringent like this opinion. [brought in Rashal; Bach; Perisha; Kneses Hgaedola; Kaf Hachaim 19/2 “One who is stringent is blessed”; The P”M 15 M”Z 2; 19 M”Z 1; M”B 15/2 write it is best not to remove Tzitzis from an old Tallis due to this reason] Vetzaruch Iyun in the change of wording in Admur ibid [“Only a Tallis that one desires to wear is obligated”] from the Michaber ibid [“So long as one is not wearing it, it is exempt”], in which one can mistakenly read the opinion of Shmuel into the wording of Admur.
 The reason: As the verse states “Asher Techaseh Bah/That you cover with”. [Admur ibid] From here we learn that Tzitzis is the obligation of a person who is wearing them and not the obligation of a garment. [Michaber 19/1; Olas Tamid 8/14; Kaf Hachaim 8/44; Vetzaruch Iyun as for why this concluding statement was omitted from Admur]
 Tana Dvei Eliyahu Rabah 26; Or Hachaim Hakadosh Shelach 15/38 in name of Yalkut
 This refers to the Jew who was caught chopping wood on Shabbos in the times of Moshe, when the Jews were in the desert. The Jew was later stoned to death for his transgression.
 Or Hachaim ibid
 Piskeiy Dinim 2/6; Rabbeinu Yonah brought in Gra 24/1
 Igros Kodesh 8/360 [brought in Shulchan Menachem 1/17]; Vetzaruch Iyun from Admur 592/7 which omits Tzitzis from the list of Mitzvos that are fulfilled at every moment, such as Tefillin and Sukkah.
 Smak; Mordechai; Rabbeinu Yonah brought in Beis Yosef; Chareidim 2 “Mitzvas Hateluyos Beiynayim” in name of Smak and Rashbatz; Yesod Veshoresh Havoda Shaar Mizrach 6 writes that Rav Chaim Vital held it is a Biblical command, and that so is proven from Rashi; See also Sefas Emes Menachos 44a; Igros Moshe 3/3; 4/4; Kinyan Torah 7/1
 Arizal in Shaar Hakavanos Tzitzis 7; Kaf Hachaim 24/11
 Kav Hayashar 45; Shemiras Halashon [end of Sefer] “One is to look at his Tzitzis a few times a day, especially when one feels forbidden thoughts coming to his mind, or feelings of anger”
 Kav Hayashar 45
 Chesed Lealafim 24/2; Kaf Hachaim 24/16
 M”A 13/8; P”M 13 A”A 8; Chayeh Adam 11/35; M”B 13/16; Poskim brought in Kaf Hachaim 13/12
 The reason: As since one is “Anus” [forced to do so against his will], it is similar to the law regarding wearing a Tallis without Tzitzis on Shabbos, in which we rule there is no Biblical prohibition against doing so being the Torah prohibits tying Tzitzis on Shabbos. [P”M ibid]
 P”M 12 A”A 7 based on M”A 13/8 and Admur 13/6
 Taz 13/5; Elya Raba 13/6; Mamar Mordechai 13/5
Ruling of Admur: Admur in chapter 13/6 omits the above ruling of the M”A ibid and writes similar to the wording of the Taz ibid, which implies to negate the opinion of the M”A and to hold that it contains a Biblical prohibition. However in 12/6 Admur rules like the M”A 12/7, that one may be lenient like the Riy [regarding measuring a torn string from the first knot] if he does not have other Tzitzis available, and the P”M ibid explains the reason behind the ruling of the M”A ibid is because when one does not have Tzitzis available it is only a Rabbinical prohibition, and by a Rabbinical prohibition one may be lenient.
 The reason: As the weekdays is a time that Tzitzis can be tied and hence even if Tzitzis is not available one may not wear a four cornered garment without Tzitzis. [Elya Raba ibid]
 19/3; M”A 19/2; M”B 19/5