* General Principle: Ghusl requires water to reach all parts of the body, including the scalp.
* Braided or Knotted Hair:
* If the hair is loosely braided or knotted such that water can easily reach the scalp without undoing the braids, most scholars say it is not necessary to unfasten it.
* If the hair is tightly braided or knotted so that water cannot easily reach the scalp, then it is obligatory to unfasten it. This is to ensure that the purification is complete.
* Length of Hair:
* Some scholars differentiate based on the length of the hair. If a woman has long hair and it is difficult to ensure water reaches the roots without loosening it, they advise loosening it.
* Other scholars don't make this distinction and stick to the principle of whether water can reach the scalp.
* Madhab (School of Thought): The specific ruling can also vary slightly based on the madhab (school of thought) followed. It's best to consult with someone knowledgeable in your specific madhab for clarification.
In summary, the core principle is ensuring water reaches the scalp during ghusl. If hair is braided or knotted in a way that prevents this, it needs to be undone. Otherwise, it is generally not required.