Judaism is an all-encompassing way of life.
The Laws of Judaism have the purpose of adding spiritual aspects to our physical natures. This is a fundamental concept of Judaism. In all physical acts, we find a way to develop and express the inner spirituality inherent in that act, while still enjoying the physical act. The Torah therefore has Laws that pertain to all areas of life.
The Torah therefore says, «Know Him in all your behavior, and He will straighten your paths» (Proverbs 3:6). This is why we have Commandments in every aspect of our lives. In everything we do, we include the divine. The Commandments thereby lift up every act we do from the mundane to the holy.
Therefore, we have Standards for everything we do. We have Standards for eating, we have Standards for talking, we have Standards for dressing, even about sleeping and going to the bathroom.
These Standards, these Laws, ensure that we bring G-d into each and every action of our lives.
Among the Standards of clothing, you can find in the Torah such Laws as not mixing wool with linen (Deuteronomy 22:11 — other fabric blends are mostly permitted, by the way), for men not to dress as women nor women as men (ibid. 22:5), and a few others. Also in that same chapter, in verse 12, you will find one of the two Biblical references to those strings we wear:
Make yourself bound tassles on the four corners of clothing with which you cover yourself.
The nature of these «bound tassles» is, of course, explained in the Oral Torah. (This, incidentally, is another example of the fact that without the Oral Torah we would never know how to keep the Commandments.)
The other mention of Tzitzis in the Written Torah is in Numbers 15:37-41. There we are taught:
Hashem told Moses, Speak to the Children of Israel and tell them that they should make «tzitzis» on the corners of their clothing. This pertains to all generations of Jews.
You shall put on the tzitzis of each corner one thread of t’chailes.
You will have these tzitzis, and when you see them you will remember all the Commandments of Hashem and you will do them, and you will not pursue the desires of you hearts or eyes.
So that you remember and do all My Commandments, and you will be holy to your G-d. For I am Hashem your G-d Who has taken you out of Egypt so that I could be your G-d.
I am Hashem your G-d.
Every Commandment that Hashem has given us comprises many different levels. We do not always know the reasons of the Commandments. Even when the Torah gives us a reason for a Commandment there are also additional deeper reasons that we may not know. This time, the Torah tells us some of the spiritual concepts in a Commandment. We are taught that if we develop self-control and fulfill the Torah’s Commandments, we will become holy and special to Hashem. That is a very important concept in Judaism.
The Torah here also teaches us that this Commandment will remind us to keep all the other Commandments. This is one reason many people wear the strings hanging out, so they can see them from time to time. (Another reason is so that the strings, which are a holy Mitzvah, are not placed next to one’s underwear.)
Each and every Commandment of the Torah helps establish our relationship with Hashem. The Torah therefore says, «So that you remember and do all My Commandments, and you will be holy to your G-d.»
Everything about tzitzis symbolizes deep concepts. For example, there are 16 strings used, four on each corner, and each corner has ten knots, which equals 26, which is the numerical value of Hashem’s Name that denotes kindness. There are many other symbolic concepts in tzitzis, but those are not the main point of the Commandment.
As far as the parameters of the Commandment itself, the Torah requires that on any four-cornered garment (of a certain minumum size) worn by a man during the day, such strings must be tied according to specific configurations. That is, the strings must be made a certain way, and they must be tied and wrapped in a certain way. They must be a minimum of a certain length, and they must be made of a specific number of strings. Even the style and number of knots is mandated to precise requirements.
Therefore, unless you know how, do not attempt to tie tzitzis on to a garment yourself. All good Judaica stores sell four-cornered garments with tzitzis already tied on them.
It is forbidden to wear a four-cornered garment without properly attached tzitzis. If they are tied incorrectly, you may not wear the garment. Even if it was done correctly, but two or more strings on even just one corner fall off or become untwisted, or if two or more strings get cut or torn until they are shorter than a certain length, you must immediately remove the entire garment. As long as you do not wear the garment, you are not required to put tzitzis on it.
There is an article of clothing made of cour corners that is standard wear for Jewish men. By wearing this, we get to fulfill the Mitzvah of Tzitzis. Many people call this garment a pair of tzitzis, or more properly, a tallis katan (which means something like «small wrap-around garment.» Many call it «arba kanfos,» which literally means «four corners.» Look here for some drawings.
In addition to the smaller four-cornered garment, the arba kanfos,» that men wear throughout the day, there is also the larger tallis, which men wear only during the morning prayers. This is also called a tallis gadol, which means something like «large wrap-around garment.» Some peoplecall this a «prayer shawl,» but it is supposed to be much larger than a shawl. The tallis, since it has four corners, must also have tzitzis, and the Laws for them are the same.
Before putting on any four-cornered garment, we must carefully check each corner to make sure the tzitzis are on correctly. For example, every morning, when we get dressed, and we put on our small «arba kanfos,» we may not put it on before we have checked to make sure the tzitzis are intact. If the tzitzis were bought from a reliable store, we do not have to check everything about the tzitzis. We just have to check that none of the strings have been torn off, and that each is at least about 1 and 1/2 inches long. If one string has torn and is now less than that length, the tzitzis are still acceptable. If two or more strings on the same corner have torn, and are both now shorter than 1 and 1/2 inches long, then the tzitzis are invalid and must be replaced. You can usually take it to a good Judaica store and ask them to do this for you for a small fee.
The same is true for a tallis, of course.
A scarf usually does not need tzitzis, since it generally is more narrow than the required minimum size. However, a very wide scarf could be a problem. As always, ask a competent Rabbi if this problem comes up.
A garment worn only during the night does not need tzitzis. However, if a man wears a daytime garment during the night, it is required to have tzitzis.
Women are therefore not required to wear tzitzis, because it is required only on a garment that is worn during the day, and thus it is a time-dependent Mitzvah. Women are exempt from most (though not all) time-dependent Positive Mitzvos.
By way of brief explanation, women themselves are enveloping creatures; men are penetrating creatures, so to speak. Women have the capability of carrying and protecting an unborn child, which men cannot do. Women are in themselves a tallis, with the ability and requirement to surround the Jewish home and family with holiness. For a deeper explanation about why women do not wear tallis and tzitzis, see the link below to my wife’s article on the subject.
The basic requirement applies only if a man happens to have a garment with four corners, and intends to wear it during the daytime. Then he is required to put tzitzis on it. If he has no such garment, there is no requirement to wear tzitzis.
But consider this: The Commandment of Tzitzis is unlike most other Commandments, in that it involves something that surrounds us. When we wear tzitzis around our torsos, holiness surrounds us from head to toe.
Therefore, the Rabbis taught that whenever possible one should try very hard to perform this Commandment, and make or purchase a garment with four corners, so he can keep the Commandment and put tzitzis on it and wear them. For after all, the Torah ties in the Mitzvah of Tzitzis with all the Mitzvos of the Torah, and says, «You will have these tzitzis, and when you see them you will remember all the Commandments of Hashem and you will do them…»
The Torah also commands that we dye one of the threads on each corner with a special blue dye, called «t’chailes.»
The Rabbis teach numerous deep concepts about this detail of the Mitzvah of Tzitzis, and I will, with Hashem’s help, cite one of them.
The Rabbis teach that the blue thread reminds us of the sky, which reminds us of the Throne of Glory of the Creator, which the Torah describes as being like sapphire, which is blue. «The saw a vision of the G-d of Israel, and under His feet was something like a sapphire brick, like the essence of a clear blue sky» (Exodus 24:10; see also Ezekiel 1:26). They did not see the Creator Himself, but only what was «under His feet,» so to speak. The blue thread reminds us of this concept, and reminds us to follow not what our heart and eyes think is correct, but after what the Creator has told us is correct.
It is forbidden to use any other dye, no matter how blue. This t’chailes was made from a creature that was called, in ancient Hebrew, «chilazon,» but no one knows for sure what that is called in English. The important thing to remember is that the blue thread is a detail in the Commandment, not the primary Commandment. Therefore, if one does not have the blue dye, one must still place tzitzis on all four-cornered daytime clothing.
For many centuries people attempted to discover the nature of this chilazon. Some respectable theories have been developed, and therefore some Rabbis have produced this dye, and their followers do indeed dye one thread on each corner with that special dye.
However, most Rabbis argue that since it is forbidden to wear any other dye on the tzitzis, we should not wear that dye, in case it is the wrong one. And after all, the blue thread is not necessary in order to fulfill the Commandment. Therefore, most Jewish men do not have the blue string on their tzitzis.
As always, one should follow one’s own Rabbi in these matters.