
Through this surah, scholars had expended the definition into a vast definition and interpretations, and one of the scholars was Al Ghazali. The introduction of the first revelation of Surah Al-'Alaq is a prove that Islam had been the pioneer in introducing the formal method in education to the children. Islam views knowledge as a very essential elements of human needs. Meanwhile, knowledge of shari'ah and knowledge of non-shari'ah matters (praiseworthy knowledge, disgraceful knowledge, and allowed knowledge) are included in the fardhu kifayah knowledge. Muamalah knowledge such as aqidah (things to do and not to) and mukasyafah knowledge are included in fardhu'ain knowledge. The results showed that in the book of Ihya' 'Ulum ad-Din, Al-Ghazali classified knowledge into two, fardhu'ain knowledge and fardhu kifayah knowledge. Fardhu'ain knowledge is a science or knowledge that is required to be studied by every human being, while fardhu kifayah knowledge is a science that if there is at least someone or a group of people who studies it, the obligation to study will fall on the communities in that area. In the book of Ihya' 'Ulum ad-Din, Al-Ghazali classified knowledge into two types, namely fardhu'ain knowledge and fardhu kifayah knowledge. Thus, knowing the meaning, object, and source of knowledge is indispensable in an education. In Islam, knowledge is the basis for worship. The sharing of knowledge is something that has long been happening in the world of Islamic education where many experts or scholars classify knowledge based on different perspectives.

Data were collected through written legacy such as writings, pictures, archives, and books about theoretical opinions, arguments, and laws related to research problems. Therefore, this study was written under the title of "The Classification of Knowledge by Al-Ghazali (A Study of Ihya' 'Ulum ad-Din Book)." Judging from the title, this scientific work is library research in which data collection technique used was documentation. This study aims to investigate the classification of knowledge according to Al-Ghazali's perspective in his book entitled Ihya' 'Ulum ad-Din. This study was initiated by the sharing of knowledge found in Islamic religious education such as the presence of fardhu 'ain and fardhu kifayah, which influence the education system in Indonesia.
