Can women trim or cut hair? What is the rule for children? My 7 yr old hair is down to thighs can i not trim?
In the name of Allāh, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-raḥmatullāhi wa-barakātuh.
Allah Ta’ala has kept a mark of beauty for women in their hair. Moreover, Rasulullah salallahu alayhi wasallam has prohibited women from shaving their hair. It is mentioned in a hadeeth,
“Rasulullah salallahu alayhi wasallam prohibited women from shaving their hair” (Sunan Tirmidhi #914)
Fuqaha’ have mentioned that it is sinful and a cause of curse for a woman to cut her hair without excuse, even if it is with the permission of one’s husband. Allamah Haskafi rahimahullah alayh has mentioned inal Durr al Mukhtar:
“If a woman cuts her hair, she will be sinful and cursed. (Fatawa) Bazzaziyah adds, “…even if it is with the permission of the husband, because there is no obedience of creation in disobedience of creator.”(al Durr al Mukhtar 6/407)
Similarly Imam Burhanud Deen rahimahullah mentions in al Muheet al Burhani fil fiqhil Nu’mani,
“When a woman shaves her hair; then if this is because of some affliction (as a means of medical treatment) then there is nothing wrong with it, (however) if she shaves in resemblance to men then it is disliked and she will be cursed due to the statement of our legislator (i.e Rasulullah salallahu alayhi wasallam).”(al Muheet al Burhani 5/377) 
Hence it is not permissible for women to cut or shave their hair, unless it is by way of medical treatment. Some Fuqaha’ have permitted trimming the hair to the length of finger tip, in order to relieve oneself from split ends and neatening the hair.
The same rule applies for those girls who are approaching puberty.If a girl of age seven (7) starts to show signs of puberty, then she should not cut her hair. But if she has not started showing signs of puberty then she may trim and fix her hair until she hits puberty or reaches the age of nine (9). However, this trimming and hair fix-up should not resemble the hairdo of kuffar (non-Muslims) or men, rather the parents should opt for hair styles which are elegant, and complement the girl being a female.
I must greatly stress the importance of tarbiyah (nurturing) for children between the age of five and fifteen (5-15). These are the years when children start interacting with the world, and absorb most of what the world has to offer. If good nurturing is provided at this stage, it is hoped that once they go on their own with their husbands, they will be confident in keeping their shar’i outlook in their lives.
My heartily advise is that the mother of the child should take it a responsibility to teach the girl ways of keeping her hair conditioned and groomed. Teach her ways of braiding and keeping the hair in control. Long hair has been a desired outlook for women in our older generation as it signifies and highlights the femininity.
The girl must learn that Islam does not inhibit taking care of one’s attire and outlook, as long as it remains within the confines of shari’ah. Teach her that the use of oils, shampoos or conditioners are all permissible. So, she can use these means and learn how to groom her self up to stay presentable and confident with the beauty Allah has given her.
As for girls who have not reached the age of puberty, nor are approaching the stage, it is permissible to trim or shorten their hair. They are not liable for the same rulings.
I sincerely make du’a that Allah showers you and your family with immense barakah, Aameen.
And Allah Ta‘ālā Knows Best
Mufti Faisal bin Abdul Hameed
Checked and concurred by
Mufti Luqman Hansrot
 أخبرنا محمد بن موسى الحرشي، قال: حدثنا أبو داود، قال: حدثنا همام، عن قتادة، عن خلاس، عن علي: نهى رسول الله صلى الله عليه وسلم أن تحلق المرأة رأسها.
(سنن النسائي, ج8,ص130,سنن الترمذي ,ج3 , ص248)
 قطعت شعر رأسها أثمت ولعنت زاد في البزازية وإن بإذن الزوج لأنه لا طاعة لمخلوق في معصية الخالق.
(الدر المختار وحاشية ابن عابدين , ج6 , ص 407)
 وإذا حلقت المرأة شعرها؛ فإن حلقت لوجع أصابها فلا بأس به، وإن حلقت تشبهاً بالرجال فهو مكروه، وهي ملعونة على لسان صاحب الشرع.
(المحيط البرهاني في الفقه النعماني , ج 5 , ص 377)
 المراهق كالبالغ
(حاشية الطحطاوي على مراقي الفلاح شرح نور الإيضاح , ص 728)
 حدثنا محمد بن بشار، حدثنا غندر، حدثنا شعبة، عن قتادة، عن عكرمة، عن ابن عباس رضي الله عنهما قال: «لعن رسول الله صلى الله عليه وسلم المتشبهين من الرجال بالنساء , والمتشبهات من النساء بالرجال .
(صحيح البخاري , ج 7 , ص 159)
 (إمداد الأحكام لإمام ظفر عثمانى , ج 4 , ص 341 )