What is the Sharee'ah ruling on shortening all the head's hair while letting that of the front part longer?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

There are four cases for shaving the head:

First: Shaving the head as a ritual of Hajj and ‘Umrah. It is a command from Allaah and the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, to do this. It is established by the Quran, the Sunnah, and the consensus of Muslim scholars. Allaah Almighty says (what means): {You will surely enter Al-Masjid Al-Haram, if Allaah wills, in safety, with your heads shaved and [hair] shortened.} [Quran 48: 27]

Second: Shaving the head for a need, as when one does so for medical purposes. This is permissible, based on evidence from the Quran, the Sunnah as well as the consensus of Muslim scholars. Allaah Almighty allows a person in the state of Ihraam (state of ritual consecration) to shave his head in case of suffering harm, even though it is not allowable to do so in the state of Ihraam. Allaah Almighty says (what means): {And do not shave your heads until the sacrificial animal has reached its place of slaughter. And whoever among you is ill or has an ailment of the head [making shaving necessary must offer] a ransom of fasting [three days] or charity or sacrifice.} [Quran 2: 196] 

Ka‘b ibn ‘Ujrah related that the Prophet, sallallaahu ‘alayhi wa sallam, passed by him while he was in a state of Ihraam and lice were falling from his head. He (the Prophet) said: "Do your lice hurt you?" Having replied in the affirmative, the Prophet, sallallaahu ‘alayhi wa sallam, said to him: "Shave your head and slaughter a sheep or fast for three days or feed six poor persons as expiation for your deed." [Al-Bukhari and Muslim]

Third: Shaving the head as an act of worship, religiousness and asceticism outside Hajj and ‘Umrah, or making shaven heads a slogan for a particular sect. It is an evil religious innovation. Describing the deviant sect of Al-Khawarij, Abu Sa‘eed narrated that the Prophet, sallallaahu ‘alayhi wa sallam, made a mention of a sect that would be among his Ummah (community), which would emerge in a time when dissension prevails among people. Their distinctive mark would be shaven heads. The Prophet, sallallaahu ‘alayhi wa sallam, said: "They would be the worst of the creatures. The group who would be nearer to the truth out of the two would kill them." [Al-Bukhari]

Fourth: Shaving the head outside Hajj and ‘Umrah but not for worship or need. The scholars provided two different opinions in this regard. Maalik held the opinion that it is disliked under the Sharee'ah. Abu Haneefah and Ash-Shaafi‘i were of the opinion that it is permissible. The latter is the preponderant opinion because the Prophet, sallallaahu ‘alayhi wa sallam, saw a boy shaving just a part of his head, and he said to him: "Shave it all or leave it all." [Ibn Hibban, Abu Daawood and An-Nasaa’i]

Shaving the head while letting the hair of the forefront longer was forbidden by the Prophet, sallallaahu ‘alayhi wa sallam, as it is stated in the Hadeeth mentioned above. The Prophet, sallallaahu ‘alayhi wa sallam, said: "Shave it all or leave it all." This is known as Qaza’ in Arabic, which means shaving a part of the head and leaving a part. Consequently, shaving a part of the head and leaving a part is impermissible in the Sharee'ah.

Allaah Knows best.