Unfortunately, many of the duʿāt (callers to Islām) are themselves unaware of (basic matters such as) what are the conditions for Prayer, or unaware of the rules and regulations concerning wuḍūʾ (ablution) and those matters which invalidate wuḍūʾ.
[Q]: There are some people here, who keep away from (attending) lessons on ʿaqīdah (creed/beliefs), and they say: ‘We are Muslims, we are not unbelievers or idol-worshippers such that we have to learn ʿaqīdah or attend lectures about it.’ So, O noble Shaykh, what is your view regarding this!
[A]: Teaching the Muslims (the correct) ʿaqīdah does not mean that we have judged them to be unbelievers. Rather, we teach the Muslims about ʿaqīdah in order for them to know about it thoroughly, and know what matters nullify it and what matters are contrary to it. Hudhayfah Ibn al-Yamān, one of the distinguished Companions – raḍī Allāhu ʿanhu – 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 ʿUmar Ibn al-Khaṭṭāb (raḍī Allāhu ʿanhu) said: “Soon the bonds of Islām will be loosened bit by bit, because people will enter into Islām but will be unaware of Jāhiliyyah (ignorant practices that Islām opposes).”  Thus, when we teach ʿaqīdah, 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 Islamic ʿaqīdah; so as to cling to it, and to be aware of what opposes it; so as to keep far away from it. Allāh – the Most High – said, whilst addressing His Prophet ṣallallāhu ʿalayhi wa-sallam: “So have knowledge about Lā ilāha illā-Allāh (i.e, have knowledge that none has the right to be worshipped except Allāh), and seek forgiveness for your sins, and for the believing men and women.” [Sūrah Muḥammad 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 Allāh! However, if one of you were asked as to what Islām means, or you were asked to explain what Islām 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 Islām, 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 Islām or īmān (faith) that the Messenger (ṣallallāhu ʿalayhi 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 duʿāʾt (callers to Islām) are themselves unaware of (basic matters such as) what are the conditions for Prayer, or unaware of the rules and regulations concerning wuḍūʾ‘ (ablution) and those matters which invalidate wuḍūʾ‘. Some of them do not even know what matters form the arkaan (pillars) of the Prayer, or form its wājibaat (obligations), or those matters which invalidate the Prayer. So what Islām are they calling to! Islām 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 Tawḥīd, since it is Tawḥīd that is the basic foundation (of both the Religion and the correct Islamic ʿaqīdah). Indeed, no one abstains from learning about Tawḥīd (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 ʿaqīdah of pure Tawḥīd, and who wishes to conceal from the people his own false beliefs, and those other deviant beliefs that are (falsely) ascribed to Islām. And this is possibly the Ease of many of those who abstain from learning about Tawḥīd. Allāh – 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.” [Sūrah al-Tawbah 9:122]
Also, the Messenger (ṣallallāhu ʿalayhi wa-sallam) said: “Whoever Allāh desires to show goodness to, He gives him the understanding of the Religion.”  The meaning of this ḥadīth is that whenever Allāh 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 ʿaqīdah.’ 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 Fatāwá (1/303-306)  Related by al-Bukhārī (no. 3606) and Muslim (no. 1847)  Related by Ibn Taymīyyah in his Majmūʿ al-Fatāwá (10/301)  Related by al-Bukhārī (1/25), from Muʿāwiyah (raḍī Allāhu ʿanhu)