According to Torah law, the commandment is that if a person wears a four-cornered garment, they must tie tzitzit to it. However, one is not obligated to acquire such a garment in order to become obligated in the mitzvah. Nevertheless, the Sages stated that a person may sometimes be punished even for not creating the conditions necessary to fulfill a mitzvah—for example, by not acquiring a four-cornered garment so as to be obligated in tzitzit. Therefore, it is proper for every male to be careful to wear tzitzit (tallit katan) throughout the day, thereby fulfilling this important mitzvah at all times. Its purpose is to serve as a constant reminder of G-d's commandments.
It is customary to be meticulous in accustoming a child to wear a tallit katan regularly from the time of his first haircut, which is traditionally done at age three. From the age of six, a child should be educated to wear a tallit katan of a minimum size of at least 50 by 50 cm.
Adapted and translated from Sichat HaShevua
