بسم الله الرحمن الرحيم
Compulsory Knowledge

What aspect of knowledge is compulsory on every Muslim (Fard `Ayn)?
 
The messenger of Allāh (sallAllāhu alayhi wasallam) said: "Seeking knowledge is a compulsion on every Muslim." This Hadeeth is referring to the knowledge of that aspect of the Deen that will save someone from the Fire. Therefore, what is important for each one of us is to be certain that we know what Knowledge is compulsory for each person to save himself from the Fire. Before discussing this, however, it is important to know that we must keep on doing righteous deeds until death, otherwise if any one changes then all the worship that he did before is going to be worthless.
 
Allāh said: "Verily, Allāh forgives not (the sin of setting up rivals in worship with Him but He forgives (sins) other than that to whom so ever He pleases..." [Al-Ourān 4:116].  This verse establishes that Allāh does not forgive shirk (i.e. setting up rivals in worship with Him), therefore the most important knowledge that a Muslim must seek is the knowledge of Shirk and all that relates to it, from Tawheed and `Aqeedah (beliefs). It is mandatory on every Muslim to learn these aspects before anything else and not listen to those who say: "These are theoretical issues, instead keep busy with matters that have action."
 
Our answer to them is that 'Aqeedah (matters relating to īmān) is the greatest of all matters in Islām because Eemān comprises of the following three aspects:
(a) believing in the heart,
(b) stating with the tongue and
(c) acting with the limbs upon what is believed in and stated.
 
All acts of worship will be rewarded based on what the heart intends for that particular action thus making it (the heart) the most important organ of the body. Belief is a practical matter because it is the action of the heart. The proof of this statement is the saying of Allāh: "...But He will call you to account for that which your hearts have earned..." [Al-Qur'ān 2:225]
 
Is there not a difference between two persons who say. "Lā ilaha illa Allāh" (there is no deity worthy of worship but Allāh), while one has a heart filled with correct beliefs, and the other is a hypocrite who disbelieves in everything in Islām? Surely there is, the first will go to Al-Jannah (Heaven) and the other will be in the lowest depth of the Fire of Hell. Why is this so? Because of the beliefs in his heart, which are its action.
 
The messenger stayed in Makkah for thirteen years inviting to 'Lā ilaha illa Allāh', and all those things that relates to it, from Tawheed, 'Aqeedah and Shirk. When the messenger sent Mu'adh to Yemen he said to him: "You are going to a people who possess a Book, so let the first thing you call them to be to testify to 'Lā ilaha illa Allāh' and if they acknowledge this, then tell them that Allāh made obligatory on them five Salawāt every day..." From the above examples we can conclude that knowing Allāh and performing Tawheed of Allāh is the most glorious knowledge in existence. Therefore, the most glorious action a person has to occupy and fill his heart with is knowing his Lord. The glory of any knowledge is based on the thing studied. Is there anything more glorious than Allāh the Glorified? Definitely not. Therefore, the knowledge that relates to the study of Allāh, what are His rights on us His creation, what He loves and what He does not would therefore be the most glorious knowledge there is in this universe.
 
Above we have proven what is compulsory knowledge for every Muslim, male or female to seek i.e. any knowledge that helps him or her to perfect their worship for Allāh.
 
The knowledge that is compulsory can be classified as follows:

1. The first obligation on any Muslim who has reached the age of maturity is to learn about the Shahadatayn i.e. "There is no deity worthy of worship but Allāh, Muhammad is the messenger of Allāh" and to understand their meanings.  That knowledge which helps us to know Allāh and teaches us His rights on us. This includes the knowledge of the 'Tawheed of Allāh' (Tawheed of Allāh's Lordship, Tawheed of His Names and Attributes and Tawheed of Worship). It also includes any knowledge that would help us to understand anything that would negate any of the above aspects of Tawheed. This would fall under the category of Shirk. Every Muslim must learn about Tawheed and Shirk.
 
2. Knowledge of His Messenger, Muhammad (sallAllāhu alyhi wasallam). This includes understanding his purpose as a messenger, his rights on us, our relationship with him. This knowledge is important because through the messenger we learn how to worship Allāh and perform His rights i.e. the messenger came to invite to tawheed and to fight mankind to keep away from worshiping other than Him.  Allāh said: "VeriIy we sent to each nation a messenger to invite to the worship of Allāh and to avoid Taghoot."
 
3. Any knowledge which helps us to know about the other four pillars of the religion namely, Salāt, Zakāt, Fasting and Hajj. Every Muslim must have knowledge about each one of them as soon as it becomes an obligation on him so that he can perform it as Allāh wants him to.
 
4. That which is Halāl and that which is Harām of social and business transactions that relates to anyone is also an obligation on him to know.
 
5. That knowledge which relates to the affairs of the heart, that which is praiseworthy and which every Muslim must try to develop and nurture, like patience, thankfulness, good character, truthfulness, sincerity, etc. and that which is blameworthy and which every Muslim must try to avoid because they are Harām and therefore can cause someone to be thrown into the Fire. Some examples of these are hatred, jealousy, pride, doing things for show, dishonesty, anger, enmity and miserliness, following the desires, etc.

As for knowledge which is Fard Kifayah; i.e. that which is a collective duty, meaning that it is not a duty on every individual, but if a group of individuals undertake to acquire this knowledge, all other individuals will be exempted from this duty, and the entire community will be free from negligence to acquire this branch of knowledge. If no one embarks on seeking this type of know1edge then the entire community is accountable.  Examples of this type of knowledge are:
– An in depth study of the Islāmic Law.
– Study of the basic sciences, industries and professions that are vital necessities for the welfare of the community like doctors of medicine, nurses, accountants, contractors, etc.

[Source: excerpted from qss.org/publications/hudaa/1.1/knowledge.html]