Question :

What is the Islamic ruling on Qaza', noting that I am a barber and most customers request it?

The Answer :

All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Qaza' is considered disliked (makruh) in Islam. It involves shaving parts of the head (with a razor or blade) and leaving other parts, or shaving scattered areas of the head. This is based on the narration of Ibn Umar (may Allah be pleased with him): "The Messenger of Allah (peace and blessings be upon him) forbade qaza'." Nafi' was asked: "What is qaza'?" He said: "It is to shave some of the head of a boy and leave some." [Agreed upon, with the wording from Muslim].
The Shafi'i scholars have interpreted the prohibition in the hadith as indicating dislike (karaha) rather than prohibition (Tahrim). Shaykh al-Islam Imam Nawawi (may Allah have mercy on him) said: "Qaza' is disliked, which is shaving part of the head, based on the hadith of Ibn Umar (may Allah be pleased with him) in the two Sahihs: 'The Messenger of Allah (peace and blessings be upon him) forbade qaza'.'" [Al-Majmu' Sharh al-Muhadhdhab, Vol. 1/P.347].
They justified the prohibition by stating that its appearance distorts the natural creation. Shaykh al-Islam Imam Nawawi (may Allah have mercy on him) said: "The scholars unanimously agree that qaza' is disliked if it involves shaving in scattered areas unless it is for medical treatment or similar reasons. It is a disliked (tanzih) practice... According to our Shafi'i school, it is disliked for both men and women without exception due to the general meaning of the hadith. The scholars stated that the wisdom behind its dislike is that it distorts the natural creation." [Sharh al-Nawawi 'ala Muslim, Vol. 14/P.101].
Therefore, cutting hair in a graded manner using scissors or a clipper is not considered qaza'; rather, it is called trimming and there is no harm in it even if the hair is of varying lengths. Shaving involves complete removal, whereas taking some of the hair while leaving part of it is called cutting. Generally, it is advisable to consider societal norms when cutting hair and to avoid strange styles that are against people's customs or resemble those of immoral people.
Accordingly, the ruling on qaza'—which involves shaving the hair with a razor or blade—is that it is disliked (makruh). It is also disliked for a barber to perform it. Observing that most of the haircuts people request do not fall under the ruling of qaza', graduated cuts using scissors or clippers without removing the hair from the root are not considered qaza'. A barber can apologize for not performing qaza' haircuts for customers, and if he does not refuse, he is not sinful but has engaged in a disliked practice. And Allah the Almighty knows best.