Nasai

Islam and human nature both require that men and women should not resemble each other in outward matters; rather, there should be a clear distinction from a distance as to who is a man and who is a woman. The Shariah has permitted men to shave their heads and cut their hair, whereas for women, neither shaving the head nor cutting the hair is permissible, so that there is no resemblance to men. In addition, long hair can also be an obstacle for men in their work and daily activities. Since women cover their heads, having long hair is not an issue for them; therefore, cutting or shaving the hair has been specified for men, and keeping the hair (on the head) has been specified for women.