As soon as a male child grows to a particular age, as for example five, the parents consult the Panchang i.e. Hindu almanac and with the assistance of the Purohit or the family priest, they select an auspicious day for the ceremony. The services of a piper with his assistants, the drummer, etc., are secured since every auspicious ceremony should have music performed by these. Certain rites are to be gone through and the father of the child is supposed to shave his son for the first time. As a razor in the hand of an inexperienced father, especially when it is sharp, must prove dangerous. So the father does its legitimate use and he simply cuts a hair or two repeating certain mantrams and entrusts his child's head and perhaps its safety and solidarity to the barber. This is done because only a barber is the right person to do so as he is expert in his art.
The portion of a garden overgrown with weeds is the portion not to be made use of. The growth of hair in one's body may be compared to the growth of weeds in a field. Scientists tell us that the sympathetic system is more developed in women than in men and the cerebro-spinal system is more developed in men than in women. Hence it may be inferred that the brain and the nervous system are generally made more use of by men than by women. Women generally use it ordinarily. The brain centres below the crown are used to a greater extent than the centres at the back. So men have their crowns shaved while women grow the hair on the head to indicate the use or otherwise of the portions of the brain.
A Grihasta shaves off the hair from every part of the body excepting the forearms, eyebrows and the tuft of hair which is considered to be an essential thing for performing certain religious ceremonies. This mainly use in the rites for the dead. At the time performing important religious rites whiskers and moustaches are considered as highly desirable.
Sanyasins shave off the hair from the whole surface of the head and the chest since they are supposed to make use of all centres in the brain including the Yoga centres. This yoga centres controlled the nervous system at the back.
Ascetics and Rishis grow hair all over their body since they are almost dead to the world and consequently no part of the body is to be made use of by them when strictly considered.