Question: Is it necessary for women to undo their plaited hair when performing ablution and ghusl? Is the situation for a woman imitating the Mâlikî or Shâfi’î Madhhab different?
ANSWER
In the Hanafî Madhhab, it is as follows:

In ablution, they can apply masah [rubbing one’s wet hands] on their hair without undoing their plaits. They do not apply masah on the hanging parts of their hair.

In ghusl, it is fard [obligatory] for a woman with plaits to moisten only the skin (scalp) of her hair. If it is possible to moisten the skin, it is not necessary to wash the plait. However, if the skin under her hair cannot be washed, then it is necessary to undo her plait. It is fard to wash all parts of the hair that is not plaited. (Radd-ul-mukhtâr)

In the Mâlikî Madhhab, it is as follows:

In ablution, she does not undo her plaited hair, and she applies masah on the whole head, including hanging parts of the hair.

In ghusl, if her scalp does not get moistened, it is necessary to undo the plait. It is fard to wash all parts of the hair that is not plaited as well. If water cannot reach the skin as a result of thickly plaited hair, then it is fard to undo the plait and to make khilâl [to comb it with fingers] of every part. (Al-muqaddamat-ul-izziyya)

In the Shâfi’î Madhhab, it is as follows:

In ablution, she applies masah without undoing her plait.

In ghusl, it is fard to undo the plait and to wet in between. (Ethics of Islam)

In the Hanbalî Madhhab, it is as follows:

In ablution, it is not necessary to undo the plait.

In ghusl, undoing the plait is sunnat when performing a ghusl to get out of the state of janâbat, but it is fard when performing a ghusl to get out of the state of haid [menstruation]. (Madhâhib-il-arba’a)