The Messenger informed Mu'adh bin Jabal, when he was going to the land of Yemen, "You are going to a people from the People of the Book. Let the first thing that you call them to be the worship of Allaah. If they acknowledge Allaah, then inform them that Allaah has obligated upon them five prayers during their days and nights" [al-Bukhaaree, Muslim].
This hadith is clear. It does not require much of an explanation. The Prophet applied this principle in his practical calling to Islam. He stayed in Makkah for thirteen years to each the people Iman and to educate his Companions on this point and to correct the beliefs of the people. That is the pattern upon which the Companions were brought up.
Jundub Ibn Abdullaah al-Bajaly said, Abdullaah ibn Umar said,
That is the manner in which the Prophet brought up his companions: Iman first and then the Qur'an. This is similar to what Imam Abu Hanifa pointed out: Understanding in the religion first (i.e. tawheed) and then understanding in the science (i.e. the sharee'ah). The beliefs must be corrected first, then follows all of the other aspects of the religion. And Imam ash-Shafi'ee said, .
al-Aqeedah linguistically is derived from the term aqada. In Arabic, one states, "Aqada the rope" when the rope is tied firmly. And, "Aqada the sale" or "He settled the sale" when the person ratifies and contracts a sale or agreement. And Alah says in the Qur'an, "And as for those whom your right hands have made a covenant (Ar.,aqadat)" [al-Nisa 33]. And Alah also says, "But He will take you to task for the oaths which you swear in earnest (Ar., aqadtum)" [al-Maida, 89] which means asserted and adhered to, as proven in the verse, "And break not oaths after the assertion of them" [an-Nahl, 91]. If one says, "Aqadtu such and such", it means his heart is firm upon such and such. Therefore, al-aqidah or al-itiqad according to the scholars of Islam is: The firm creed that one's heart is fixed upon without any wavering or doubt. It excludes any supposition, doubt or suspicion.
Imam Abu Hanifa called this great subject al-Fiqh al-Akbar ("The Greater Understanding") and the understanding of the religion. He called the science of law (Ar., sharee'ah) the understanding of the science. Many scholars of Islaam use the word tawheed for all matters that a person must believe in. This is because the most important of these matters is the basic tawheed that is contained in the phrase, "There is none worthy of worship except Alah".
Tawheed, according to them, may be divided into two categories: tawheed of cognition and affirmation and tawheed of purpose and deeds. Tawheed of cognition and affirmation is the tawheed of the Oneness of the Creator and the tawheed of His Names and Attributes [i.e. He is Unique in His being the only Creator and the only One with His names and attributes]. Tawheed of purpose and deeds s tawheed of lordship or that none should be worshipped except Alah [i.e., He is the only One worthy of worship].
The scholastic theologians (Ar., kalaamiyoon) - and what will explain to you who the scholastic theologians are - call this great subject "the root of the religion" and they call the law "the branches of the religion". This is their terminology. We also have a dispute with them in this matter but this is not the place to discuss it. all of them give it a name or adjective according to their needs. But what is the name the Qur'an gives to this matter?
The Qur'an gives the grave matter the name Iman. Alah says in the Qur'an, "And thus We inspired in You (Muhammad) a Spirit of Our command. You did not know what the Scripture was, nor what the Faith was. But we have made it a light whereby We guide whom We will of our bondmen..." [al-Shura, 52].
The general concepts that the heart of the believer must be firm about are the "pillars" of this faith. But one will not be called a believer just by knowing and understanding these pillars but he must come to the level where he submits and implements what is described, in the hadith of Gabriel, as Islam. Iman, in this manner, incorporates Islam.
If Iman was simply knowing the facts in one's heart, then its companion would be equal to Satan and Pharaoh [Note: The Satan was the most knowledgeable of his Lord but he was destroyed because of his pride and envy. And Pharaoh, even though he claimed to be the lord, knew that the lord is Alah and that none has the right to be worshipped but Him. Alah says, "He said: In truth you know that none sent down these portents save the Lord of the heavens and the earth as proofs..." [al-Isra, 102]. - Although they knew the truth, they did not put it in practice by turning their 'ibadah to Alah Alone].
In the hadith of Gabriel, the Prophet explained the pillars of this faith in which every human must believe, when he was asked, "What is Iman?", he said, "To believe in Alah and His angels and His books and His messengers and the Last Day and predestination of good and evil".
It is a must for every person to know these pillars and to learn them with a correct understanding and to believe in them in the manner that he pious forefathers understood and believed in them, in the same manner that the Companions of the Prophet believed and understood them, as well as their Followers and those who followed on their path. This includes the four Imams, Sufyan Al-Thauri, Sufyan ibn Uyaina, Abdullah ibn al-Mubarak and others similar to them, as well as Muhammad ibn Ismail al-Bukhaaree, Muslim ibn Al-Hajjaj, Shaikh al-Islam ibn Taymiya and al-Hafedh ibn al-Qayyim. And scholars similar to them who followed the same manner of understanding and believing in these pillars.
This is the first obligation upon the responsible human being. There is no difference of opinion on this question among the scholars whose opinions are worth following. Imam Abu-Hanifa said, . What he meant by faith is tawheed and what he meant by science is the sharee'ah. He put the understanding of tawheed before the understanding of the sharee'ah.
And Shaikh al-Islam al-Haruwi al-Ansari (d. 481 AH) stated at the beginning of his book, Itiqad ahl al-Sunnah, 'You will come to a people from the People of the Book. The first thing that you should call them to is the worship of Alah. If they gain the knowledge of Alah, then tell them that Alah obligates upon them five prayers during the day and night...'"
From this premise did the great scholars of Islam precede. Ponder, for example, what Imam Muhammad ibn Ismail al-Bukhaaree did in his book al-Jami al-Sahih, which is the most authentic book after the Book of Alah; one will see that from his detailed knowledge and understanding of this religion, this great Imam began his book with "The Beginning of Revelation" and then he followed it with chapters on faith, followed by the chapters on knowledge. As if he means, may Alah have mercy on him, to point out that the first obligation upon a human being is faith or Iman and the way to attaining faith is knowledge. And the source of faith and knowledge is revelation. So he began by showing how the revelation occurred and what it was like. Then he followed by mentioning faith and knowledge. This arrangement is no accident; by it he makes some important points.
This is the sum of what we wish to mention and what we wish to raise our voices about. The matter of aqeedah is the first priority. Faith and knowledge are the means of attaining it. And the source of knowledge and faith is the Book and Sunnah.
Source: Importance of Aqeedah