There is a unanimous agreement among Muslim scholars that washing the hair is obligatory for both men and women when performing ghusl. However, the woman who has braids or plaits is not obliged to unbraid them when performing ghusl after intercourse. Rather, she can pour water over them till water reaches the roots of the hair and the scalp. The Prophet, peace and blessings be upon him, is reported to have addressed Umm Salamah, may Allah be pleased with her saying, “It is sufficient to pour water over your head three times and then pour it over your whole body three times, and with that your Ghusl is completed.”
It means that what is to be done is washing the hair till the water reaches the scalp, and it is not sufficient to wipe over the hair without washing it thoroughly unless there is a clear sign that washing the hair will cause physical harm for the woman. A reliable physician determines such case, and this gives a woman an excuse to wipe over the hair, without washing. In other words, what is important is wash the hair until water reaches the scalp irrespective of the hairstyle the woman is doing.
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, who states:
“A lady needs to wash her hair with water but she needs not undo the plaited hair; it is sufficient for her to pour water over your head.
It is common knowledge that following sexual intercourse, both men and women are obligated to perform a complete ghusl (ritual bath) in order to be eligible to worship.
A complete ghusl involves washing the entire body including one’s hair; if however, due to medical or health reasons, one is advised by a physician not to wash the hair, then one should not wash the same. In such cases it is enough to wash the rest of the body and do tayammum (dry ablution) in lieu of the parts one has not washed.”