One of the categories of knowledge is the unseen knowledge of the Quran mentioned in the Holy Book. We'll examine a few verses that go into more detail about this kind of knowledge.
Only God Has Access to the Unseen 

Say, ‘No one in the heavens or the earth knows the Unseen except Allah, and they are not aware when they will be resurrected.’ 1

Everything else originates from Allah, who alone possesses knowledge of the unseen in an independent and limitless form.

One of the things that only God knows is when the Day of Judgement will arrive, and no one else does. 2

God refutes the deities worshipped by the polytheists in this verse. The argument goes that their gods do not know the unseen, the Day of Judgement, or the date of their resurrection. The deity and God must oversee the matters of those who worship Him, including the rewards and punishments on the Day of Judgement, even though none of the creations are aware of this.

They have to know the day and date as a result. But none of them are gods because none of them—not even the jinn, angels, or saints among humans—know about this day. 
He Discloses This Information to Some

Knower of the Unseen, He does not disclose His [knowledge of the] Unseen to anyone except to an apostle He approves of. Then He dispatches a sentinel before and behind him. 4

The first of these two verses states that God gives no one access to the unseen. Ihr(), or disclosure/exposure, helps someone else come to a conclusion and incorporate it.

Therefore, God states that I do not help anyone to dominate or encompass my unseen. It is exclusive to God and not shared with anyone else that He is aware of everything invisible. Thus, the entire meaning of the verse is refuted.

He does, however, make an exception to the previous "anyone" in the following verse. He clarifies that He distributes this knowledge to any prophet He pleases, to the degree that He pleases.

Consequently, we can conclude that knowledge of the invisible is fundamentally and exclusively God's. Nevertheless, others may be able to acquire it if God so chooses and instructs them. 5

A Quality of a Believer

Who believe in the Unseen, maintain the prayer, and spend out of what We have provided for them. 6

Shahda, which means "perceived," is in contrast to the word ghaib, which means "unseen." The term "unseen" alludes to God and His greatest manifestations, including revelation, all concealed from our senses.

Though revelation or the hereafter are mentioned separately in the next verse, belief in the unseen in this verse refers to belief in God.

The verses of the Quran keep reminding believers to follow good intelligence and pure reasoning rather than limit themselves to sensory and material things.