Believe in the existence of the jinn is not a prerequisite of faith, which for example, is the belief in angels. However, it would be more correct to consider this issue in the context of faith in the book of the Creator.
Believe in the book of the Creator means that we recognize it, including that of the Holy Quran is the message of Allah, revealed through the angel Jibraeel (alayhi salam) to the Prophet Muhammad (peace be upon him). Accordingly, we accept and agree with the fact that all the commandments of Allah, transmitted through the Quran, are mandatory for us and not voidable truths.
For example, it is clearly divided that is a permitted and the forbidden in the Quran. However, faith in reverse, that is called forbidden permitted, may cause person exit from Islam. And if a person is not consciously perceive the prohibitions prescribed in the Quran, the prohibition of eating pork, alcohol use, gambling, he may be among the lost faith. We need to clearly realize that Islam is an inseparable integral whole. It is impossible to divide the laws and principles of Islam, and say at the same time that you are a believer, but perceive only some of them, while others do not accept and deny. If a person receives written in the Quran prescription forbidden and permitted, as the truth, but rejects and refuses to believe in the existence of such creations as the jinn, about which clearly said in this same Scripture, then this may lead to the most disastrous results, until turning him into a kafir. May Allah preserve us from that.
“And I did not create the jinn and mankind except to worship Me”. (The Quran, 51:56)
“And [mention, O Muhammad], when We directed to you a few of the jinn, listening to the Qur'an. And when they attended it, they said, "Listen quietly." And when it was concluded, they went back to their people as warners”. (The Quran, 46:29)
Imam Alusi in his Tafseer “Ruhul-Maani” said about those who deny the existence of the jinn: “Denying the existence of the jinn there is an open kufr” (Tafsirulb-Alusi, 29\82).
Ibn Hazm also believes that: “anyone who denies the existence of the jinn, he is clearly kafir”. (Ibni Hazm Al-Faslu fil milyali val ahvali van nihal, 5\12)
The Mufti of the Republic of Tatarstan Kamil hazrat Samigullin