Muslims have to keep on learning from the cradle to the grave. The knowledge which Muslims have to learn is called al-'Ulum al-Islamiyya (Islamic sciences), which consist of two parts:
I) al-'Ulum an-naqliyya, II) al-'Ulum al-'aqliyya.
I) Al-'Ulum an-naqliyya (also called 'religious sciences'): These sciences are acquired by reading the books of the 'ulama' of the Ahl as-Sunnat. The 'ulama' of Islam derived these sciences from four main sources. These four sources are called al-adillat ash-Shariyya. They are al-Qur'an al-karim, al-Hadith ash-Sharif, ijma' al-Umma and qiyas al-fuqaha'.
Religious sciences consist of eight main branches:
1) 'ilm at-tafsir (the science of interpretation of Qur'an al-karim). A specialist in this branch is called a mufassir; he is a profoundly learned scholar able to understand what Allahu ta'ala means in His Word.
2) 'ilm al-usul al-hadith. This branch deals with classification of hadiths. Different kinds of hadiths are explained in Endless Bliss, second fascicle, sixth chapter.
3) 'ilm al-hadith. This branch studies minutely the sayings (hadith), behavior (sunnat), and manners (hals) of our Prophet (sall-Allahu 'alaihi wa sallam).
4) 'ilm al-usul al-kalam. This branch studies the methods by which 'ilm al-kalam is derived from al-Qur'an al-karim and al-Hadith ash-Sharif.
5) 'ilm al-kalam. This branch covers the study of the kalimat at-tawhid and the kalimat ash-shahada and the six fundamentals of iman, which depend on them. These are the teachings to be believed in by heart. Scholars of kalam usually wrote 'ilm al-usul al-kalam and 'ilm al-kalam together. Therefore, the layman takes these two branches of knowledge as one single branch.
6) 'ilm al-usul al-fiqh. This branch studies the derivation of the methods of fiqh from Qur'an al-karim and Hadith ash-Sharif.
7) 'ilm al-fiqh. This branch studies afal al-mukallafin, that is, it tells how those who are sane and pubescent should act on matters concerning the body. This is the knowledge necessary for the body. Afal al-mukallafin has eight sections: fard, wajib, sunnat, mustahab, mubah, haram, makruh and mufsid. However, they can be briefly classified into three groups: actions commanded, actions prohibited and actions permitted (mubah).
8) 'ilm at-tasawwuf. This branch is also called 'ilm al-ahlak (ethics). It explains not only the things we should do and we should not do with the heart but also helps the belief to be heartfelt, makes it easy for Muslims to carry out their duties as taught in 'ilm al-fiqh and helps one attain marifa.
It is fard-i 'ain for every Muslim, man or woman, to learn kalam, fiqh and tasawwuf as much as necessary out of these eight branches, and it is a guilt, a sin, not to learn them.
II) Al-'Ulum al-aqliyya (also called 'experimental sciences'): These sciences are divided into two groups: technical sciences and literary sciences. It is fard kifaya for Muslims to learn these sciences. As for Islamic sciences, it is fard 'ain to learn as much as is necessary. To learn more than is necessary, that is, to become specialized in Islamic sciences is fard kifaya. If there is no alim who knows these sciences in a town, all of its inhabitants and government authorities will be sinful.
Religious teachings do not change in the course of time. Making a mistake or erring while commenting on 'ilm al-kalam is not an excuse but a crime. In matters pertaining to fiqh, the variations and facilities shown by Islam can be utilized when one has the excuses shown by Islam. It is never permissible to make alterations or to make reforms in religious matters with one's own opinion or point of view. It causes one to go out of Islam. Change, improvement and progress in al-'Ulum al-'aqliyya are permissible. It is necessary to develop them by searching, finding and even by learning them from non-Muslim, too.
The word 'fiqh', when used in the form of 'faqiha yafqahu', that is, in the fourth category, means 'to know, to understand.' When it is used in the fifth category, it means 'to know, to understand Islam.' A scholar in 'ilm al-fiqh is called a faqih. 'Ilm al-fiqh deals with the actions which people should do and those which they should not do. The knowledge of fiqh is composed of Qur'an al-karim, Hadith ash-Sharif, ijma' and qiyas. The consensus of the as-Sahabat al-kiram and the mujtahids who came after them is called ijma' al-Umma. The rules of the religion derived from Qur'an al-karim, Hadith ash-Sharif and ijma' al-Umma are called qiyas al-fuqaha.' If it could not be understood from Qur'an al-karim or Hadith ash-Sharif whether an action was halal (permitted) or haram (forbidden), then this action was compared to another action which was known. This comparison was called qiyas. Applying qiyas required the latter action to have the same factor which made the former action permitted or forbidden. And this could be judged only by those profound 'ulama' who had attained the grade of ijtihad.
'Ilm al-fiqh is very extensive. It has four main divisions:
1) 'ibadat, composed of five subdivisions: salat (namaz), sawm (fast), zakat, hajj, jihad. Each has many sections. As it is seen, it is an 'ibada to make preparations for jihad. Our Prophet (sall-Allahu 'alaihi wa sallam) explained that jihad against the enemies of Islam was of two kinds: by actions and by words. It is fard to learn how to make and use new weapons in preparation for jihad by actions. Jihad is done by the State. It is fard for the people to join the jihad by obeying the State's laws and orders concerning jihad. Nowadays, enemy assault through publications, motion pictures, radio broadcast and every means of propaganda -the second kind of war- has tremendously increased; therefore it is also jihad to stand against the enemies in this field.
2) munakahat, composed of subdivisions, such as marriage, divorce, alimony and many others [written in detail in the book Se'adet-i Ebediyye].
3) muamalat, composed of many subdivisions, such as purchase, sale, rent, joint-ownership, interest, inheritance, etc.
4) uqubat (penal code), composed of five main subdivisions: qisas (lex talionis), sirqat (theft), zina (fornication and adultery), qadhf (accusing a virtuous woman of incontinence) and ridda (the case of becoming an apostate).
It is fard for every Muslim to learn the 'ibadat part of fiqh sufficiently. It is fard kifaya to learn munakahat and muamalat; in other words, those who have anything to do with them should learn them. After 'ilm at-tafsir, 'ilm al-hadith and 'ilm al-kalam, the most honorable ilm is 'ilm al-fiqh. The following six hadiths will be enough to indicate the honor of fiqh and the faqih: 'rahmatullahi ta'ala alaihim ajmain'
'If Allahu ta'ala wants to bestow His blessing on a slave of His, He makes a faqih of him.'
'If a person becomes a faqih, Allahu ta'ala sends what he wishes and his sustenance through unexpected sources.'
'The person about whom Allahu ta'ala says 'most superior' is a faqih in the religion.'
'Against Satan, a faqih is more stoic than one thousand 'abids (those who worship much).'
'Everything has a pillar to base itself upon. The basic pillar of the religion is the knowledge of fiqh.'
'The best and most valuable 'ibada is to learn and teach fiqh.'
Superiority of al-Imam al-azam Abu Hanifa (rahmat-Allahi ta'ala 'alaih) is also understood from these hadiths.
Rules of Islam in the Hanafi Madhhab were transmitted through a chain beginning with 'Abdullah ibn Masud (radi-Allahu 'anh), who was a Sahabi. Al-Imam al-azam Abu Hanifa (rahmat-Allahi ta'ala 'alaih), the founder of the Madhhab, acquired the knowledge of fiqh from Hammad, and Hammad from Ibrahim an-Nakhai. Ibrahim an-Nakhai was taught by Alqama, and Alqama studied under Abdullah ibn Masud, who was educated by Rasulullah (sall-Allahu 'alaihi wa sallam).
Al-Imam al-azam Abu Hanifa (rahmat-Allahi 'alaih) compiled the knowledge of fiqh, classified it into branches and sub-branches, and set usuls (methods) for it. He also collected the knowledge of itiqad as Rasulullah (sall-Allahu 'alaihi wa sallam) and the as-Sahabat al-kiram (ridwan-Allahi 'alaihim ajmain) had preached, and taught them to hundreds of his disciples. Some of his disciples became specialists in 'ilm al-kalam, that is, in the teachings of iman. Of them, Abu Bakr al-Jurjani, one of Imam Muhammad ash-Shaibani's disciples, became famous. And Abu Nasr al-'Iyad, one of his pupils, educated Abu Mansur al-Maturidi in 'ilm al-kalam. Abu Mansur wrote in his books the knowledge of kalam as it came from al-Imam al-azam (rahmat-Allahi ta'ala 'alaih). By contending against heretics, he consolidated the itiqad of the Ahl as-Sunnat. He disseminated it out far and wide. He passed away in Samarqand in 333 (944 A.D.). This great alim and another alim, Abu 'l-Hasan al-Ashari, are called the imams of the Madhhabs of itiqad of the Ahl as-Sunnat.
The fiqh scholars are grouped in seven grades. Kamal Pasha Zhada Ahmad ibn Sulaiman Effendi (rahmat-Allahi ta'ala 'alaih), in his work Waqf an-niyyat, explained these seven grades as follows:
1. The mujtahids of Islam, who constructed the methods and principles of deriving tenets from the four sources of the religion (Adilla-i arba'a), and derived tenets in accordance with the principles they established. The four aimmat al-madhahib were of these.
2. The mujtahids in a Madhhab, who, following the principles formulated by the imam of the Madhhab, derived rules from the four sources. They were Imam Abu Yusuf, Imam Muhammad, etc. (rahmat-Allahi ta'ala 'alaihim ajmain).
3. The mujtahids of matters (masala), who for the matters that were not dealt with by the founder of the Madhhab, derived rules using the methods and principles of the Madhhab. Yet in doing this, they had to follow the imam. They were at-Tahawi (238-321 A.H., in Egypt), Hassaf Ahmad ibn 'Umar (d. 261, in Baghdad), 'Abdullah ibn Husain al-Karkhi (340), Shams al-aimma al-Halwani (456, in Bukhara), Shams al-aimma as-Sarahsi (483), Fakhr-ul Islam 'Ali ibn Muhammad al-Pazdawi (400-482, in Samarqand), Qadi-Khan Hasan ibn Mansur al-Farghani (592), etc. (rahmat-Allahi ta'ala 'alaihim ajmain).
4. Ashab at-takhrij, who were not able to employ ijtihad. They were scholars who explained in brief, unclear rules derived by mujtahids. Husam ad-din ar-Razi 'Ali ibn Ahmad (d. 593 A.H., in Damascus) was one of them. He (rahmat-Allahi ta'ala 'alaih) wrote a commentary to Al-Quduri.
5. Arbab at-Tarjih, who preferred one of the several riwayas (narrations or opinions of the mujtahids as narrated) coming from mujtahids. They were Abu l'Hasan al-Quduri (362-428 A.H., in Baghdad) and Burhan ad-din 'Ali al-Marghinani the author of Al-hidaya, who was martyred by the soldiers of Genghis in the Bukhara Massacre of 593 A.H. [1198 A.D.].
6. Those who wrote various riwayas about a matter in an order with respect to their reliability were called muqallids. They did not include any refused riwaya in their books. Abu 'l-Barakat 'Abdullah ibn Ahmad an-Nasafi (d. 710 A.H.), the author of Kanz ad-daqaiq; 'Abdullah ibn Mahmud al-Musuli (d. 683), the author of Mukhtar; Burhan ash-Sharia Mahmud ibn Sadr ash-Sharia 'Ubaid-Allah (d. 673), the author of Al-wiqaya; and Ibn as-Sa'ati Ahmad ibn 'Ali al-Baghdadi (d. 694), the author of Majma' al-bahrain, are of these (rahmat-Allahi ta'ala 'alaihim ajmain).
7. They are also muqallids incapable of distinguishing weak riwayas from genuine ones.
 Kimya' as-Saada. Muhammad al-Ghazali (rahmat-Allahi ta'ala 'alaih) was one of the greatest Islamic scholars. He wrote hundreds of books. All his books are very valuable. He was born in 450 (1068 A.D.) in Tus, i.e. Meshed, Persia, and passed away there in 505 (1111 A.D.).
 He was born in Baskal'a in 1281 (1864 A.D.) and passed away in Ankara in 1362 (1943 A.D.).
 The 'ulama of Ahl as-Sunnat collected 'ilm at-tasawwuf by learning this second task of our Prophet ('alaihi 's-salam) from the Twelve Imams (rahmat-Allahi ta'ala 'alaihim). Some people do not believe in awliya', karamat or tasawwuf. This shows that they have no connection with the Twelve Imams. If they had followed the Ahl al-Bait, they would have learned this second task of our Prophet from the twelve Imams and there would have been many scholars of tasawwuf and awliya' among them. But there have not been any, and besides, they do not even believe that such scholars could exist. It is obvious that the Twelve Imams are the Ahl as-Sunnat's imams. It is the Ahl as-Sunnat who love the Ahl al-Bait and follow the Twelve Imams. To become a scholar of Islam, one has to be an heir of Rasulullah ('alaihi 's-salam) in these two tasks. That is, one has to be an expert in these two branches of knowledge. 'Abd al-Ghani an-Nabulusi (rahmat-Allahi ta'ala 'alaih), one of such scholars, quoted, on pages 233 and 649 in his work Al-Hadiqat an-nadiyya, the hadiths describing the spiritual rules of Qur'an al-karim and pointed out that disbelieving these rules indicates ignorance and misfortune.
 Al-Hadiqa, p. 323 and in preface to Radd al-mukhtar.
 These were counted among fiqh scholars because they could understand what they read and explained it to the muqallids who could not understand.