Untied or loose hair is considered bad or inauspiciousness in Hinduism as it invites negative energy and destruction. Loose and open hair is a symbol of death and mourning.
During puja and when entering temple, the hair should be tied and not left loose.
Even while sleeping, it is advised to keep the hair tied.
Untied or loose hair is also a symbol of sex, thus a women shows united hair only to her husband.
In the Ramayana, Sita’s mother Sunayana advices her to keep the hair always neatly tied as it a symbol of bond and auspiciousness.
Never Pull a Woman by her Hair
Ravana had pulled Sita by her united hair to the Pushpak Vimana while kidnapping her. The result of which was the complete destruction of the demons.
Again Dushasana had dragged Draupadi by her loose hair to the court of Hastinapura. The result of which was the complete annihilation of the Kaurava clan. Draupadi had taken the vow that she will only tie her hair after it was anointed with the blood of Dushasana.
Kamsa attempted to kill the eighth girl child of Devaki by lifting the baby by its hair. The girl child escaped from the hands of Kamsa and predicted his downfall.
All these are the reasons why untied or loose hair is considered bad or inauspiciousness in Hinduism.