The first obligation upon each and every accountable person is to know about Allah, Exalted be He.
The evidence for this is noted in the following Statement of Allah, Most High (interpretation of meaning), "So, know O Prophet that there is no god ?worthy of worship? except Allah. And seek forgiveness for your shortcomings and for? the sins of? the believing men and women." (Quran 74:19) Al-Bukhari made a section with the title of, “Knowledge comes before action and words” under which he listed the ayah and commented on it by saying, “Allah has mentioned knowledge first”. [1] Saheeh al-Bukhaaree (1\24)
Ibn al-Qayyim commented on the ayah by saying, “Knowing about Allah’s Oneness and that there is no god worthy of worship except Him is necessarily required by itself. However, having this knowledge alone is insufficient because it must be coupled with worshipping Allah alone without associating any partner with Him in worship. It is necessarily required to know the Names, Attributes, Actions and Rules of Allah, and to worship Him according to them because as worshipping Allah is required by itself, knowing about Him is also equally required by itself.” [2] Muftaah Daar al-Sa’adah (1/178)
It is narrated on the authority of ‘Uthmaan ibn ‘Affaan (may Allah be pleased with him) that the Prophet (صلى الله عليه وسلم) said, “Whoever died truly knowing that there is no god worthy of worship except Allah alone will enter Paradise.” [3] Saheeh Muslim (26) This report explains the merit of knowing the words of Monotheism and the virtue of dying upon it. The opposite of knowledge is ignorance; it is the vehicle through which some Muslims deviated and thus contradicted its meaning and refrained from acting upon it. [4] See Zad al-Ma’ad (p. 56)
It was related that Ali ibn al-Hasan ibn Shaqeeq asked Ibn Al-Mubarak: "How do we know our Lord?" He said: «By (knowing) that He is above the seventh Heaven over His Throne. We do not say as the Jahmis say that He is here on earth.” [5] Al-Sunnah of Abdullah ibn Ahmad ibn Hanbal (1\111)
Aboo Bakr al-Khawarizmee said, “Explaining that it is an obligation to know about Allah, Exalted be He, as established by the Quran and the consensus of the Muslims. As for the Quran, Allah, Most High, said (interpretation of meaning), "So, know O Prophet that there is no god? worthy of worship? except Allah (Quran 74:19), Know that Allah is your Protector (Quran 8:40), "Say, ?O Prophet? “Consider all that is in the heavens and the earth!” (Quran 10:101) "And Indeed, in the creation of the heavens and the earth…" (Quran 2:164) The Quran is full of similar parts to the extent scholars stated there are 300 ayahs, all of which call upon us to contemplate and learn, and the consensus is established on this matter.” [6] Mufeed al-‘Uloom wa Mubeed al-Humoom (p. 19)
Ismael al-Asbahaanee said: “The scholars of the righteous predecessors (as-Salaf) stated that the first obligation that Allah has dictated upon His slaves is sincerity, which is to know and acknowledge Allah, and obey His orders and prohibitions. The first of it is to testify that there is none worthy of worship except Allah alone and that He is has no partner, and that Muhammad (صلى الله عليه وسلم) is His slave and Messenger.” [7] Al-Hujja Fi Bayan al-Hujjah (2/279)
Ibn Taymiyyah said, “The knowers of Allah have always been in agreement that no person can perfect his knowledge about Allah or even supplicate and turn to Him perfectly without affirming that He is above everything else. By this affirmation, they also agree that the belief that Allah is the only god worthy of worship will become deep-rooted in his heart, and that he will have a Lord that he turns to and worships. Otherwise, without it, certainty about having a God that he worships, and turns to, will not find its way into his heart as doubt and confusion will persist in his heart, which can be confirmed by anyone whose heart experienced any of these causes.” [8] See Bayan Talbees al-Jahmiyyah (4/555)
Ibn Jama’ah said, “The knowledge of Monotheism is about knowing Allah and believing in Him, knowing that which He is entitled to, and knowing what is not right or appropriate to say about Him. Not only is it a part of the sixth pillars of Imaan but also associated with it. Indeed, it is the noblest of all knowledge and the most honoured in the sight of Allah, the Most High, because the level of honour of a knowledge emerges from the object of knowledge (i.e. Allah.). However, this is provided that this knowledge does not deviate from the meanings indicated in the Quran and authentic Sunnah, the consensus of credible scholars, and the understanding of sound intellects within the limits of Islamic rules as well as the rules of authentic Arabic language.” [9] Iydaah al-Daleel fi Qat’ Hijaj Ahl al-Ta’teel (page 7)
Ibn al-Qayyim said, “No person will ever be deep-rooted in knowledge, let alone Imaan, except after he believes in the Attributes of the Lord, Exalted be He, and knows about them so well that he no longer be considered ignorant about his Lord.” [10] Madarij al-Salikeen (3/324)
Ibn Rajab said, “No heart can be reformed before it knows Allah, loves Him, glorifies Him, fears Him, hopes from Him, and relies upon Him so well that they are well settled in the heart. This is the true meaning of monotheism and the real translation of the testimony that there is no god worthy of worship except Allah. A heart is only reformed when its God that it worships, loves, and fears is Allah alone, without any partner.” [11] Jami’ al-‘Uloom wal Hikam (1\211)
Ibn al-Wazeer said, “Knowing Allah is evident in one’s innate nature and its existence precedes doubt, as Allah, Most High, said, "Their messengers asked ?them?, “Is there any doubt about Allah, the Originator of the heavens and the earth? (Quran 14:10) and the Prophet (صلى الله عليه وسلم) said, “Each child is born with a sound innate nature.” [12] Al-‘Awasim wal Qawasim fil Dhab ‘An Sunnat Aboo al-Qasim (3/394)
Ibn ‘Uthaymeen said: “Knowing Allah, Exalted be He, is of two kinds: (i) knowing about His existence and the meanings He wanted us to know, and (ii) knowing His Essence and Reality. The former is that which we are required to learn whereas the latter is not dictated upon us, because nobody knows the reality of His Essence or His Attributes. Mind you, it is impossible to acquire this kind of knowledge.” [13] See Sharh al-‘Aqeedah al-Safareeniyya (1\147)