Hence it is clear from what has been stated so far, the knowledge we are referring to is the Religious Knowledge of Islam. Moreover, this knowledge of the Religion entails many facets and many subjects; the knowledge of tawhid and the knowledge of the rules of the Religion are among them.
*The knowledge of tawhid entails knowing about Allah and His Messenger, and it is the best of all the knowledge in Islam. The scholars repeatedly emphasized the clear evidences from the Qur'an, hadith, and scholarly consensus proving the knowledge of tawhid is ranked the highest among all knowledge. This is so because it has to do with knowing about Allah and about His Messenger--knowing what befits Allah and what is impossible to be among His attributes and what befits the messengers and what would be impossible to be among the attributes of the messengers. *
Imam AbuHanifah said: "Tawhid is the 'Great Knowledge (al-fiqhul akbar)."Imam ash-Shafi^iyysaid: "I mastered the knowledge of Tawhid before mastering the knowledge of the rules of the Religion."
This knowledge of tawhid is of two categories. The first category is that which is obligatory on every accountable person, (The accountable person is the one who is pubescent, sane, and has heard the Testification of Faith in a language he understands.) The accountable person is obligated to know this knowledge; hence, this category is classified among the Personal Obligatory Knowledge. Examples of this knowledge include the belief in Allah and the belief in His angels, His Books, His Messengers, the Day of Judgment, Destiny, and the like. The second category of this knowledge of tawhid is that which is obligatory that some Muslims master--but not all Muslims. This obligation is classified as a communal obligation, since if some of the Muslims have that knowledge it is no longer an obligation on the rest of the community. Examples of this category is for one to learn the proofs of the tenants of belief from the Qur'an, hadith, and intellect such that one would have the ability to refute the claims of the enemies of Islam--like the communists and the innovators of misguidance. Also among the communal obligations some Muslims must acquire are the sciences Muslims need--such as medicine, engineering, agriculture, and the like. Hence, if enough Muslims learn these sciences such that they satisfy the need of the community, it is no longer obligatory on the others.
The first category of the knowledge of tawhid, the personal obligation, has two subdivisions. The first subdivision entails knowing correctly about Allah and His Messenger and believing in it beyond doubt. If one does not know and believe this, he would not be a Muslim, and he would not escape the everlasting tortures of Hellfire. However, having satisfied this and having uttered the Testification of Faith at least once in his lifetime, but not capturing other essentials of belief and not fulfilling other obligations such as fasting and praying and the like, he would be a sinful Muslim--provided he does not deny the obligation of fasting, praying, and the like. The second subdivision entails learning the thirteen attributes of the Self of Allah which are obligatory on every accountable person to know and learning the attributes of the prophets and what follows, such as believing in the angels of Allah, the Books of Allah, the Messengers of Allah, the Day of Judgment, Destiny--what is good and evil--Paradise, and the like. If having satisfied this, one will earn for his acceptable deeds.
As to the rules of the Religion, part of this knowledge is a personal obligation. The Muslim who is accountable is obligated to learn the matters of purification (taharah), the rules of prayers, the rules of fasting, and the rules of other obligations that apply to him, like Zakat, Pilgrimage, dealings, sins of the body, and the like.
*Learning the Obligatory Knowledge of the Religion makes one able to discriminate between what is lawful (halal) and what is unlawful (haram), what is valid and what is invalid, what is acceptable and what is rejected, in addition to what is classified under the Religion as good or bad. The scholars of Islam have spoken explicitly about these criteria. In the chapter entitled "Knowledge Before Saying or Committing Action," Imam alBukhariyy stated: "If one acquires the Obligatory Knowledge of the Religion, one acquires the ability to differentiate between what is lawful and what is unlawful, what is acceptable and what is not acceptable, and what is good and what is evil."
Allah said in the Qur'an in Surat at-Tahrim,Ayah 6:
which means: [O believers, protect yourselves and your families from Hellfire which is fueled by people and stone.] Imam ^Ata' Ibn Abi Rabahwho was among the followers of the Companions, interpreted that verse of the Qur'an.
He said: "One protects himself and his family from the tortures of Hellfire by learning how to pray, fast, sell, buy, marry, and divorce."*