A: A Mazhab refers to a religious school of thought that is followed in matters pertaining Fiqh and jurisprudence. There were many Mazhabs and leaders of Fiqh and Jurisprudence in the past but only four have thrived and survived because of their codification and expertise that have stood out for over 13 centuries.
We are commanded to follow the Quraan and Sunnah. It is indeed difficult for the ordinary layman who is not well-versed in the Quraan and Hadith and their related sciences to study, grasp and have a thorough understanding of every aspect of the Quraan and Hadith based on their individual study. It is for this reason that the Quraan Shareef instructs us to ask the people of knowledge if we do not know, rather than advising us to make our own deductions from the Quraan and Hadith based on independent research which requires many pre-requisites and conditions many of which an ordinary person does not fulfill and hence does not have the capacity to undertake. This directive of the Holy Quran is a great mercy upon the Ummah as it creates ease in following the deductions of learned scholars rather than imposing self-study of which one does not have the ability to undertake.
It had taken scholars years of studies and dedication to obtain such expertise and proficiency. In fact, every scholar of every generation is heavily and deeply indebted to his tutors and elders right through until the Sahabaah Kiraam (R.A.), who learnt, preserved and passed on these to us.
In some way or the other, even those who advocate not following a Mazhab in some subtle way follow someone or the other.
The adherence to one of the four Mazhabs simply refers to an ordinary layman being convinced of the following aspects regarding the Imaam he is adhering to;
1. Being most closely and accurately following the Quraan and Sunnah
2. Having outstanding qualities of righteousness and piety and not being motivated by wealth or position.
3. His Fiqh and teachings being well codified that enables his followers to easily practice on his verdicts and rulings.
Should a person wish to come out of his Mazhab or pick and choose between the Mazhabs then amongst the general masses this is mostly done to suit one's whims and fancies rather than it being based on valid Shari evidence, as such a person does not generally have the necessary knowledge and proofs to soundly prove that the Imaam he follows is not the most accurate in a particular ruling. Further, if he does so because of a certain apparent Hadith that is quoted to him in isolation then he has done so based on his limited knowledge rather than basing his proposed change on an overall understanding of all the sciences of the Shariah.
We strongly recommend that you refer to the book, The Legal Status of Following a Mazhab, by the Honourable Mufti Muhammad Taqi Usmani. You may access this book from the following link: http://www.scribd.com/doc/30858160/The-Legal-Status-of-Following-a-Madhab-by-Sheikh-Mufti-Taqi-Usmani-PDF
Shafique Jakhura (Mufti) MD Mangera (Mufti)