Islam has two main sources: the Holy Qur’an and the Sunnah which is the biography of the Messenger of Allah (peace and blessings of Allah be upon him) and his hadith (sayings)
During the first three centuries, the Sunnah scholars endeavored to derive rulings on belief, worship, transactions and ethics from these two sources. These imams’ efforts culminated in four schools of jurisprudence that differed in some particulars related to worship and transactions.
Each of the four schools is attributed to one of the four founders. They are: Imam Abū Ḥanīfa (who died in Baghdad in 767 AD/150 AH), Imam Mālek (who died in Medina in 795 AD/179 AH), Imam Shāficī (who died in Egypt in 820 AD/204 AH) and Imam Ibn Ḥanbal (who died in Baghdad in 855 AD/241 AH).
The map of schools of jurisprudence has been geographically established since the early centuries, based on each people’s choice while respecting other people’s choices.
These choices were defined as the religious constants in the jurisprudence of each country or several countries.