1: The undoubted believe in ALLAH
For a muslim, to believe in ALLAH is the first and the most important thing. If a person does not reject other gods, and still believes in other gods, he is not a muslim and commits shirk. ALLAH is the one and only God, who was not created, neither born nor commanded by any other god. He was from forever and He will remain forever. There is no time that can define HIS existence neither any space that can measure HIM.
Al-Quran 4:116
“Indeed, Allah does not (ever) forgive ‘shirk’ _ (the sin of associating partners with Him) _ anything else He will forgive for whomever He wills. He, who commits ‘shirk’ has in fact lost his way, and has gone far astray!”
2: Angels
Angles are the purest creatures of ALLAH swt who do the tasks commanded by ALLAH swt. They are more in number than us and they are praying ALLAH swt day and night. They do not feel tired of praising ALLAH swt. They are made of nor i.e. the blessed and pure light.
Al-Quran 2:098
“Whoever is the enemy of Allah, His angels, His messengers, (angels) Gibrael and Mikael (should know that) indeed, Allah is the enemy of those who reject the truth.”
3: Prophets
ALLAH swt sent 1,24000 prophets to guide the mankind. These prophets were chosen among the tribes and nation whom they guided. The distict characteristic of prophets was that they were the most pious, God fearing and most knowledgeable among the people they lived with.
Al-Quran 2:136
“(Oh believers)! say, “We believe in Allah and the revelation sent to us, as well as the revelation sent towards Ibraheem, Ismail, Ishaque, Yaqub and the tribes. (We believe in) that which was given to Musa and Jesus, and (also) that which was given to (other) prophets by their Lord. We do not discriminate against any of them. To Him, we have surrendered completely.””
4: the Day of Judgment
The last hour will come, and will bring the judgment day. Every Prophet warned His nation about the Day of Judgment. And they tried to prepare for the Day of Judgment. This day the book of deeds of every human will be handed to him and he will be sent to face ALLAH swt and will be judged according to his deeds. There is no doubt about the coming of this day. The belief in this day means that we believe that somebody is there who created us and who is capable of destroying everything in the blink of eyes.
Al-Quran 3:025
How then will it be with them, when we shall gather them together at the day of judgment, of which there is no doubt; and every soul shall be paid that which it hath gained, neither shall they be treated unjustly?
5: fate
One of the most important belief is in fate or decree. To be a follower of islam means to believe in the fate i.e. the fate of every human is written in the loh-e mehfooz. But there should not be asked too many questions about it because it is such a complex matter that brings many doubts in the mind whenever thought. But a pre written fate does not mean that humans are not given free will. The fate must be believed keeping in mind the provision of “freedom of will”. ALLAH swt has given us choices, HE has given us the free hand to be good or bad. So the matter of fate gets complex because to understand it, we need a very right state of mind with a realization of what we actually are. If we are any capable of doing things at our end, that capability is pre written.
The matter of fate is discussed in Quran in form of the story of Prophet Moses a.s and Prophet Khizer s.a. this event shows that the fate was known to khizer a.s. and moses a.s. was not knowing this.
6: jins
Jins are also creature of ALLAH swt like humans and animals and birds. To reject their existence is to reject the creation of ALLAH which is kufr. Jinns exists in many religions like we exist on earth. jins live in another dimension different than us. it is mentioned in tafsir ibn’ kathir that before humans, there used to live jinns on earth. satan is also a jin. Jins are made of fire.
15:027
“And We had earlier fashioned jin from a hot sultry flame!”