The description of ghusl

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that "when he took a bath, he would splash water into both his eyes and insert his finger into his navel (to make the water reach it)."
This narration is sahih (authentic) and mawquf (a Companion's statement). Imam Malik narrated it through Nafi'; it has also been narrated as marfu' (attributed to the Prophet), but that is not established.

Shu'bah (may Allah have mercy on him) relates about Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that "when he took the bath for janabah (major impurity), he would pour water with his right hand onto his left hand seven times."
Imam Abu Dawud narrated it.

It is narrated from Sayyiduna Umar al-Faruq (may Allah be pleased with him) that he said (regarding the method of ghusl): "As for me, I pour three handfuls (of water) over my head."
The chain of this report is sahih (authentic), and Imam Musaddad bin Musarhad narrated it in his Musnad; it is evidence that pouring water over the whole head three times in ghusl is a Sunnah and recommended practice.

It is narrated from Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) that a man asked him about the bath for janabah, and he said: "Three times (pouring water is sufficient)." The man said (in surprise): My hair is very thick? Sayyiduna Abu Sa'id (may Allah be pleased with him) said: "The blessed hair of the Messenger of Allah (peace and blessings be upon him) was far thicker than yours and supremely pure and fragrant."
Imam Abu Bakr bin Abi Shaybah narrated this hadith; the narrator Atiyyah al-Awfi in its chain is da'if (weak), but the basis of pouring water three times in ghusl is established by other authentic hadith.

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the delegation of the tribe of Thaqif said: "O Messenger of Allah! Our land is a cold region, so what (amount of water or method) will suffice us for the bath for janabah?" The Prophet (peace and blessings be upon him) said: "As for me, I pour water over my head three times (when bathing)."
Imam Abu Ya'la narrated it from Ibn Abi Saminah, he from Mu'tamir bin Sulayman, with this same chain.
This hadith is sahih (authentic).

It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that a man asked the Prophet (peace and blessings be upon him) about a man who takes the bath for janabah but some part of his body is missed by the water. The Messenger of Allah (peace and blessings be upon him) said: "He should wash that place and then pray."
This hadith was recorded by Imam al-Daraqutni (748) and Imam al-Bazzar (1560); its chain contains a narrator named Jabir bin Saylan, who is majhul (unknown), on account of which this narration is weak in its chain.

It is narrated from Na'im (may Allah have mercy on him), the freed slave of Sayyidah Umm Salamah (may Allah be pleased with her): I asked the Mother of the Believers Sayyidah Umm Salamah (may Allah be pleased with her) about a man's ghusl, and she said: "He should clean his hair well and drench his skin thoroughly with water." And I asked her about a woman's ghusl, and she said: "She should clean the skin of her scalp well, but she does not need to undo her (braided) hair."
This report describes the manner of the bath for janabah: in ghusl it is necessary to make water reach the roots of the hair and the whole skin; however, if a woman has plaited her hair into braids, it is sufficient for her merely to make water reach the skin of the scalp, and undoing the hair is not obligatory.