Question: The questioner from Jeddah says: Is washing the head enter into the ghusl of Janabah or is washing the body enough?
Answer: “It is obligatory in the ghusl of Janabah to cover the entire body [with water] for men and women The Prophet (ﷺ) used to pour water over his hair three times [al-Bukhari (no. 254) and Muslim (no. 327)]. And when Umm Salamah (may Allah be pleased with her) asked him: “Should I undo the hair on my head for Janabah? He (ﷺ) said: ‘No’. [Sunan at-Tirmidhi (no. 105) and an-Nasaai (no. 241)]. So he (ﷺ) did not command her to undo the hair of the head however he commanded her to pour water over her head and cover all the head with water. The Mother of the Believers asked: ‘Do I have to undo [the hair on my head]’. He (ﷺ) said: ‘No you do not have to undo it’ which proves that they used to immerse the head with water. However it was hard upon them to undo the hair so the Prophet (ﷺ) did not command her to undo it. So it proves the obligation of immersing/soaking the head of the hair with water and it is not obligatory to undo [the hair]”
Faisal bin Abdul Qaadir bin Hassan