Question:

I heard that many Chassidic Jews prefer to wear woolen tzitzit, as opposed to cotton, which is much more comfortable. Why?

Response:

In the Talmud, there is an opinion that one is Biblically obligated to affix tzitzit, the ritual fringes that are on the corners of the prayer shawl, onto a wool or linen garment only.

This is learned from a verse where it states in regards to a specific law involving clothing,1 “a woolen garment, or on a linen garment.”2 From here some learn that when it says “garment” in the Bible in the context of a commandment, it is referring specifically to wool and linen garments. Therefore, the commandment to place fringes on a four-cornered garment—“You shall make yourself twisted threads, on the four corners of your garment with which you cover yourself”—is referring specifically to a wool or linen garment.3

According to this tradition, placing fringes on garments made of other materials, such as silk, is a rabbinical requirement, not a Biblical one.4

In his gloss on the Code of Jewish Law, Rabbi Moshe Isserles, known as the Rema, rules that garments of all fabrics are equally Biblically required to have fringes.5

Nonetheless, it is preferable to wear a prayer shawl that is made of wool,6 since it is Biblically required according to all opinions.7

But, you ask, if there are reliable rabbinic authorities who rule that cotton is okay, why sweat with wool? I guess the key here is that mitzvahs are more than just paying dues to the Great Supernal I.R.S. We do them because we love Him. Sure your spouse can subside on tuna and crackers, but serving them their favorite dishes transforms it into an act of love. And wearing the kind of garment that we are sure warrants a mitzvah does the same thing.