How should a man’s hair be cut?

Shaykh Muhammad ibn Ibraaheem was asked about that and he said: 

With regard to hair, the Prophet’s guidance is either to leave it all alone or to remove all of it. He did not shave part of it and leave part of it. 

What some Muslims do, which is to shave part of the head and leave part, is the qaza’ (tuft) which was forbidden by the Prophet (peace and blessings of Allaah be upon him). This may take several forms: 

1-Shaving some parts of the head and leaving others

2-Shaving the sides of the head and leaving the middle

3-Shaving the middle and leaving the sides

4-Shaving the front and leaving the back

5-Shaving the back and leaving the front

6-Shaving one side and leaving the other

The fact that these types are haraam is indicated by the report in al-Saheehayn from Ibn ‘Umar (may Allaah be pleased with him) who said, “The Messenger of Allaah (peace and blessings of Allaah be upon him) forbade qaza’, i.e., shaving parts of a boy’s hair and leaving other parts.” And it was narrated from him (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) saw a boy who had some of his hair shaved and some left; he forbade them from doing that and said: “Shave it all or leave it all.” And it was narrated from ‘Umar (may Allaah be pleased with him) in a marfoo’ report (i.e., attributed to the Prophet (peace and blessings of Allaah be upon him)): “Shaving the back of the head, unless it is for the purpose of cupping, is the act of the Magians.” In Sunan Abi Dawood it is narrated that Anas ibn Maalik (may Allah be pleased with him) saw a boy with his head shaved, leaving two braids or long locks, and he said, “Shave these or cut them, for this is the style of the Jews.” Al-Marwadhi said, “I asked Abu ‘Abd-Allaah (i.e., Ahmad ibn Hanbal) about shaving the back of the head, and he said, “That is what the Magians do, and whoever imitates a people is one of them.”