The hairstyle of the Prophet (peace and blessings of Allaah be upon him) is mentioned in a number of ahaadeeth, such as the following: 

1 – His hair was neither curly nor straight. 

It was narrated that Anas ibn Maalik said, describing the Prophet (peace and blessings of Allaah be upon him), he was of average height, neither very tall nor very short. He had a ruddy complexion, neither very white nor very dark, and his hair was neither curly nor straight. The revelation came to him when he was forty years old.

 (Narrated by al-Bukhaari, 3354; Muslim, 2338) 

2 – His hair came down to his earlobes. 

It was narrated that al-Bara’ ibn ‘Aazib (may Allaah hbe pleased with him) said: The Prophet (peace and blessings of Allaah be upon him) was of average height and broad shouldered. He had hair that came down to his earlobes. I saw him wearing a red garment and I never saw anyone more handsome than him. 

Narrated by al-Bukhaari, 3358; Muslim, 2337 

3 – His hair sometimes came down to his shoulders 

It was narrated that Qutaadah said: I asked Anas ibn Maalik (may Allaah be pleased with him) about the hair of the Messenger of Allaah (peace and blessings of Allaah be upon him). He said, The hair of the Messenger of Allaah (peace and blessings of Allaah be upon him) was neither curly nor straight, and came down to a point between his ears and his shoulders.  

Narrated by al-Bukhaari, 5565; Muslim, 2337 

According to another report, his hair used to touch his shoulders. 

Narrated by al-Bukhaari, 5563; Muslim, 2338 

Sometimes his hair was shorter than that. All of this may be understood as referring to different situations, and each of the Sahaabah narrated what he had seen. 

4 – The Prophet (peace and blessings of Allaah be upon him) used to dye his hair sometimes. 

It was narrated that ‘Uthmaan ibn ‘Abd-Allaah ibn Moohib said: I entered upon Umm Salamah and she brought out to us one of the hairs of the Prophet (peace and blessings of Allaah be upon him) which was dyed. 

Narrated by al-Bukhaari, 5558. 

Ahmad (25328) added: … dyed with henna and katam. 

Katam is a plant that is used to dye the hair. When mixed with henna it gives the hair a colour between black and red. See ‘Awn al-Ma’bood, commentary on hadeeth no. 4205 

5 – He used to part his hair. 

It was narrated from ‘Ibn ‘Abbaas (may Allaah be pleased with him) that the Messenger of Allaah (peace and blessings of Allaah be upon him) used to let his hair hang down over his forehead and the mushrikoon used to part their hair, and the People of the Book used to let their hair hang down over their foreheads. The Messenger of Allaah (peace and blessings of Allaah be upon him) liked to be like the People of the Book in matters where there was no specific command. Then the Messenger of Allaah (peace and blessings of Allaah be upon him) parted his hair.  

(Narrated by al-Bukhaari, 3365; Muslim, 2336). Some of the scholars discussed the meaning of this hadeeth, and their comments were summed up by Imam al-Nawawi as follows: 

The correct view is that both letting the hair hang down over the forehead and parting it are permissible, but that parting is better. 

Sharh Muslim, 15/90 

6 – The Prophet (peace and blessings of Allaah be upon him) did his Farewell Pilgrimage when his hair was stuck together. 

(This means) making some parts of the hair stick to others using gum or something similar, so that the hair is held together and avoids getting dirty and does not need to be washed. This is easier for the person who is in ihraam, especially in the past when the person in ihram was faced with a lot of dirt and little water. 

It was narrated that Ibn ‘Umar (may Allaah be pleased with him) said: I saw the Messenger of Allaah (peace and blessings of Allaah be upon him) raising his voice in the Talbiyah, with his hair stuck together. 

Narrated by al-Bukhaari, 5570; Muslim, 1184 

7 – The Prophet (peace and blessings of Allaah be upon him) sometimes used to braid his hair, especially when travelling, to keep it from getting dusty. 

It was narrated that Umm Haani’ said: The Prophet (peace and blessings of Allaah be upon him) came from Makkah with four braids. 

Narrated by al-Tirmidhi, 1781; Abu Dawood, 4191; Ibn Maajah, 3631. Classed as saheeh by al-Haafiz Ibn Hajar in Fath al-Baari, 10/360. 

With regard to the kinds of hairstyles that are forbidden, they are characterized by the following:                                                                                                  

1 – al-Qaza’ (lit. tufts), which is where part of the head is shaved and part is left. 

It was narrated from Ibn ‘Umar that the Messenger of Allaah (peace and blessings of Allaah be upon him) forbade al-qaza’. 

Narrated by al-Bukhaari, 5466; Muslim, 3959. 

One of the narrators of this hadeeth defines al-qaza’ as shaving part of a child’s head and leaving some of his hair. 

Ibn al-Qayyim (may Allaah have mercy on him) said: 

With regard to shaving part of the head and leaving part, this is of varying degrees. 

The worst is shaving the middle of the head and leaving the sides, as the Christian monks do. 

After that comes shaving the sides and leaving the middle, as many of the foolish and worthless people do. 

After that comes shaving the front of the head and leaving the back. 

These three types all come under the heading of qaza’ which was forbidden by the Messenger of Allaah (peace and blessings of Allaah be upon him), but some of them are worse than others. 

Ahkaam Ahl al-Dhimmah, 3/1294 

2 – Imitating the kaafirs or immoral people. 

There are many such hairstyles, some of which come under the heading of qaza’ – such as the “Marines” haircut, which is forbidden for two reasons, the fact that it is a kind of qaza’ and the fact that it is an imitation of the kuffaar. Some of them do not involve qaza’ but they are styles that belong to the kuffaar, such as making some of the hair stand up and letting the rest hang down, and so on. 

This also includes every hairstyle that belongs to the kaafirs or immoral people, because it is not permissible for a Muslim to resemble them in that, because the Prophet (peace and blessings of Allaah be upon him) said, “Whoever imitates a people is one of them.” 

Narrated by Abu Dawood, 4031. Classed as hasan by al-Haafiz ibn Hajar in Fath al-Baari, 10/271. its isnaad was classed as jayyid by Shaykh al-Islam in Iqtida’ al-Siraat al-Mustaqeem, p. 82. 

Shaykh al-Islam said: 

The least that we can say about this hadeeth is that it implies that it is haraam to imitate them, although the apparent meaning is that the one who imitates them is a kaafir, as in the verse (interpretation of the meaning): 

“And if any amongst you takes them (as Awliyaa’), then surely, he is one of them”

[al-Maa’idah 5:51] 

Iqtida’ al-Siraat al-Mustaqeem, p. 83. 

Imitating foolish people. 

These are hairstyles worn by some of the foolish people, which may be included in the categories mentioned above. 

See also question no. 14051 

And Allaah knows best.