Why you need to Learn ‘Aqeedah ?
Unfortunately, many of the du’aat (callers to Islaam) are themselves unaware of (basic matters such as) what are the conditions for Prayer, or unaware of the rules and regulations concerning wudoo‘ (ablution) and those matters which invalidate wudoo‘.
[Q]: There are some people here, who keep away from (attending) lessons on ’aqeedah (creed/beliefs), and they say: ‘We are Muslims, we are not unbelievers or idol-worshippers such that we have to learn ’aqeedah or attend lectures about it.’ So, O noble Shaykh, what is your view regarding this!
[A]: Teaching the Muslims (the correct) ’aqeedah does not mean that we have judged them to be unbelievers. Rather, we teach the Muslims about ’aqeedah in order for them to know about it thoroughly, and know what matters nullify it and what matters are contrary to it. Hudhayfah Ibnul-Yamaan, one of the distinguished Companions – radiyallaahu ’anhu – said:
“People used to ask the Messenger about the good, but I used to ask him about the evil, for fear of falling into it.” 
Likewise ’Umar Ibnul-Khattaab (radiyallaahu ’anhu) said: “Soon the bonds of Islaam will be loosened bit by bit, because people will enter into Islaam but will be unaware of Jaahiliyyah (ignorant practices that Islaam opposes).” 
Thus, when we teach ’aqeedah, this does not imply that we have judged those whom we are teaching to be non-Muslims. Rather, what it means is that we desire that they should be thoroughly aware of the correct Islaamic ’aqeedah; so as to cling to it, and to be aware of what opposes it; so as to keep far away from it. Allaah – the Most High – said, whilst addressing His Prophet sallallaahu ‘alayhi wa sallam:
“So have knowledge about Laa ilaaha illallaah (i.e, have knowledge that none has the right to be worshipped except Allaah), and seek forgiveness for your sins, and for the believing men and women.” [Soorah Muhammad 47:19]
So it is essential that a person learns and that he does not content himself with merely saying: ‘I am a Muslim.’ Yes indeed, you are a Muslim – and all praise is for Allaah! However, if one of you were asked as to what Islaam means, or you were asked to explain what Islaam is, then many of you would not be able to correctly explain this. If one of you were to be asked to explain what are those factors which nullify Islaam, then many of you would not be able to explain this. Thus, if a person is ignorant (of such fundamentals), it is possible that he may fall into falsehood without realizing it. If one of you were asked to explain the pillars of Islaam or eemaan (faith) that the Messenger (sallallaahu ’alayhi wa sallam) explained and taught, we would find that most people would be unable to do so. So how is it that a person (suffices with) saying: ‘I am a Muslim,’ yet does not know these (basic) matters!
Unfortunately, many of the du’aat (callers to Islaam) are themselves unaware of (basic matters such as) what are the conditions for Prayer, or unaware of the rules and regulations concerning wudoo‘ (ablution) and those matters which invalidate wudoo‘. Some of them do not even know what matters form the arkaan (pillars) of the Prayer, or form itswaajibaat (obligations), or those matters which invalidate the Prayer. So what Islaam are they calling to! Islaam is not merely a call, rather it is a reality to be learnt and practiced. So it is essential to acquire sound knowledge and understanding of the Religion. This is because a person who does not have sound knowledge, may fall into dangers without even realizing it; just like a person who walks down a path, but is ignorant of the fact that along this path there is a ditch, or a hole, or even an ambush. Yet (due to his ignorance) he ends up falling into the hole, or the ambush, without even realizing it.
Thus it is essential to learn about Tawheed, since it is Tawheed that is the basic foundation (of both the Religion and the correct Islaamic ’aqeedah). Indeed, no one abstains from learning about Tawheed (and those matters it necessitates, as well as its limits, conditions, fundamentals, clear proofs, fruits and consequences, and those matters which increase and strengthen it, and those that decrease and weaken it, etc.) except one of two people: [i] an ignorant person – and the ignorant person’s [view] is not to be given any weight; or [ii] a bigoted deviant – one who desires to avert people from the ’aqeedah of pure Tawheed, and who wishes to conceal from the people his own false beliefs, and those other deviant beliefs that are (falsely) ascribed to Islaam. And this is possibly the Ease of many of those who abstain from learning about Tawheed. Allaah – the Most High – said:
“And it is not proper for all the Believers to go out together and fight. From every troop of them only a party of them should go forth, so that those who remain behind may gain understanding of the Religion so that they may (instruct and) warn their people when they return to them, in order that they may beware.” [Sooratut-Tawbah 9:122]
Also, the Messenger (sallallaahu ’alayhi wa sallam) said: “Whoever Allaah desires to show goodness to, He gives him the understanding of the Religion.”  The meaning of this hadeeth is that whenever Allaah does not want to show goodness to a person, He does not give him the understanding of the Religion. So the one who says: ‘I do not need to learn ’aqeedah.’ It is as if he is saying: ‘I do not need to gain understanding of the Religion!’ And this is said by either an ignorant person, or one who is misguided!
 al-Muntaqaa min Fataawaa (1/303-306)
 Related by al-Bukhaaree (no. 3606) and Muslim (no. 1847)
 Related by Ibn Taymiyyah in his Majmoo’ul-Fataawaa (10/301)
 Related by al-Bukhaaree (1/25), from Mu’aawiyah (radiyallaahu ’anhu)