Reader: I would like some information on the custom of an Upshirin (boy's first haircut at three). What is the reason behind the custom? And what is done at the Upshirin? Thanks
Mesora: I have not seen a source in Judaism endorsing the common practice of waiting for a child's third birthday to cut his hair. In it of itself it carries no sense and has no connection with any halacha. There used to be a custom to wait to cut the child's hair the first time (which could be any age) and they would cut the hair and leave the payis long to teach of the law of payis. They would wait until the Regel, (Holiday) so the holiday's gladness would be increased. But no where does it say one must wait until 3 years of age. We must be careful not to add onto the law which G-d has given us. This is an open command in the Torah, not to add, and not to subtract.
I feel certain rituals from other cultures have seeped into Judaism, such as wearing red bendels (which is assur according to an open Tosephta in Shabbos, Perek 7), and inserting kapituls into the Western Wall, which is contrary to a pasuk at the end of Parshas Yisro, "bkol makom asher azkir es shmi, avo alecha uvarachticha", "in all places where My name is mentioned, I will come to you and bless you". This shows us clearly that G-d is cognizant of our actions no matter where we are. We are no closer to G-d when we are in Israel. Physical proximity does not play a role in closeness to G-d. There certainly are benefits outlined in the Talmud for living in Israel, but a wicked person has no more merits if he moves there. Additionally, our prayers are no more heard when written on paper and stuck in a wall, than if uttered in Osh Kosh.
Reader 2: You mention you don't know the source for the minhag. It is taken from a Zohar that combines Deut. 20:19 and Lev. 19:23. There are deeper reasons for it as well.
Mesora: Zohar cannot create minhag, as minhag does not work that way. Minhag means a "way" of performing halacha. Therefore, unless there is an existing halacha with its source in the talmud, there can be no minhag, a way of performing some new practice.
People today misconstrue what minhag is. They feel it is like a Torah law which requires no other source than itself, but this is false.
For example: There is a Torah law not to eat milk and meat together. The Rabbis then enacted a protective device - a "gzaira" - which is that one must wait a specific time between eating meat and milk. Only once this law existed of "waiting", can there be different minhagim (customs) of how long one will wait, and these are based on principles. But if there was never a rabbinic law of waiting, there could be no minhag of waiting, as minhag cannot be baseless.
Similarly, there are no laws pertaining to cutting a child's hair, therefore there cannot be a minhag about how. Most people will disagree as this touches on a sensitive issue of the tenderness and innocence of a child, and a family get together. However, Torah has specific rule and upshirin does not qualify as minhag, or rabbinic law, and certainly not Torah law.