[The Divine Knowledges for Which No Muslim is Excused]

Answer – and Allah is the One who grants success and help: The knowledges that are indispensable, and without which faith and Islam are not complete, are as follows:
1. Knowing Allah, Mighty and Majestic, with the heart, then acknowledging [that] with the tongue.
2. Belief in the Messenger (May Allah bless him and his family and grant them peace) and in the Qur’an and what it contains; and following that, belief in all of the messengers of Allah, exalted is He, and in what was sent down upon them from Allah; and belief in the angels of Allah. It is not a condition to know the messengers by their names and the names of their Books, nor to know the types of angels or some of their names.
3. Knowledge of the Last Day, and belief in it and in what it contains of reward for the obedient in Gardens of bliss wherein they will abide forever, and of punishment for the sinners who rebel against Allah in the Fire of Hell wherein they will abide forever.
4. Then, after that, it is necessary to know the people of truth and to affiliate oneself with them in religion, exactly as Allah, exalted is He, said: “O you who have believed, fear Allah and be with the truthful.” [Al-Tawbah:119]
He does not need to know the disputed issues, nor to know the truth in every single issue; rather, it suffices him to affiliate himself with the people of truth, to believe that he follows their religion, and that he says what they say in general.
The proof for this is what we have observed from the scholars of the Ahl al-Bayt (Peace be upon them): that they approved, in general, of their followers and those affiliated with them, upon what they were of affiliation in general.
Among the completeness of faith and Islam is yielding and submitting to Allah, glorified is He, and complying with Him by performing the obligations and avoiding the prohibitions. Allah, exalted is He, has described the faith of the Messenger (May Allah bless him and his family and grant them peace) and the believers, saying, majestic is His affair: “The Messenger has believed in what was revealed to him from his Lord, and [so have] the believers. All of them have believed in Allah and His angels and His Books and His Messengers, [saying], ‘We make no distinction between any of His Messengers.’ And they say, ‘We hear and we obey. [Grant us] Your forgiveness, our Lord; and to You is the destination.’” [Al-Baqarah:285]
Yes, faith in Allah, exalted is He, and belief in Him does not require seeking or exertion. Indeed, every newborn is born upon the natural disposition (fitrah). For this reason we see that once a child reaches the stage of understanding and discernment, he searches by his innate disposition, and is drawn by his nature, to seeking and asking: “From where was I born? From where did I come? Who created me?” These questions continue to revolve in his mind until he reaches his aim of knowing Allah and believing in Him.
Children often direct these questions insistently to their mothers. From here came the hadith: “Every newborn is born upon the fitrah, until his parents make him a Jew, or a Christian, or a Magian.”
What also supports what we have mentioned—that faith in Allah, exalted is He, is part of the fitrah and does not require seeking or exertion—is that Allah, glorified and exalted is He, very often says, after setting forth the signs that indicate His divinity and Lordship: “Will you not reason?” and “Will you not remember?” This indicates that knowledge of Allah, exalted is He, is established for those who possess intellects, and that the rational person needs no more than to return to his intellect and recall the knowledge embedded in his innate disposition, if he has forgotten or been heedless.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.3