My hair is very long… Do I have to wash all of my hair when performing the purity shower after menstruation or janābah? Or is it sufficient to wash only the scalp, especially when I need to leave the house and it becomes difficult for me to wait for my hair to dry completely so I can wrap it?

Answer

Praise Be to Allah and Peace Be Upon His Messenger.

With reference to your question quoted above, the jurists have agreed that intention and ensuring that water reaches all of the hair and skin are obligations of ghusl  (the purity shower). ʿĀʾishah (may Allah be pleased with her), the wife of the Prophet (peace and blessings be upon him), said:

Whenever the Prophet (PBUH) took a bath after Janaba he started by washing his hands and then performed ablution like that for the prayer. After that he would put his fingers in water and move the roots of his hair with them, and then pour three handfuls of water over his head and then pour water all over his body.

This hadith combines what is obligatory and what is recommended in ghusl. Its method is that one washes the hands before placing them into the vessel, then pours water with the right hand over the left to wash the private parts, then performs a full ablution as for prayer, then parts the hair and pours three handfuls of water over the head, then pours water over the right side of the body and then over the left. This is the most complete and preferred form of ghusl.

There is no difference between men and women in how ghusl is performed, except that scholars differed regarding whether a woman must undo her braided hair when performing ghusl for janābah or menstruation. The correct view — adopted by the majority of the Ḥanafīs, Mālikīs, Shāfiʿīs, and Ḥanbalīs — is that it is not required to undo braided hair as long as water reaches the roots of the hair.

Umm Salamah (may Allah be pleased with her) said:
“I said: O Messenger of Allah, I am a woman who ties her hair tightly; should I undo it for ghusl after janābah?”
He said: “No, it is enough for you to pour three handfuls of water over your head, then pour water over your whole body, and you will be purified.”
(Sahih Muslim, Book of Menstruation, Chapter: Ruling on the braids of a woman performing ghusl)

However, if the hair is matted, extremely thick, or tightly braided such that water cannot penetrate it, then it must be undone.

Therefore, in ghusl after janābah, water must reach the roots of the hair and the scalp; wiping is not sufficient. Water should also reach the entire length of the hair, even if it is long.