Among the evidence of Ahl al-Sunnah is:
The ayah/verse (interpretation of the meaning):
“… but the shayateen (devils) disbelieved, teaching men magic and such things that came down at Babylon to the two angels, Harut and Marut, but neither of these two (angels) taught anyone (such things) till they had said, “We are for trial, so disbelieve not (by learning this magic from us).” And from these (angels) people learn that by which they cause separation between man and his wife, but they could not thus harm anyone except by Allah’s leave. And they learn that which harms them and profits them not.” [2:102]
This ayah clearly indicates what is being asked about here, which is that witchcraft is real and that the practitioner of witchcraft can cause separation between a man and his wife and that he can cause harm to people by his witchcraft – if that is decreed by the universal will of Allah.
Jabir quoted the Prophet (peace and blessing upon him) as saying:''
Most of the deaths of my people, after Allah's Qadha(Preordainment) and Qadar(Destiny), are caused by the evil eye.''
Transmitted by Al-Bukhari in At-Tarikh, and classed by Sheikh Albani as authentic in Sahih Al-Jami'(4144)
''The Prophet (peace be upon him) used to tell me to seek Ruqya against the evil eye.''
Al-Bukhari: 10/170 and Muslim: 2195
“And verily, those who disbelieve would almost make you slip with their eyes
Ibn ‘Abbaas and others said, commenting on this verse: this means, they put the evil eye on you with their glances.
The Prophet (peace and blessings of Allaah be upon him) said: “The evil eye is real and if anything were to overtake the divine decree, it would be the evil eye. When you are asked to take a bath (to provide a cure) from the influence of the evil eye, you should take a bath.”
Narrated by Muslim. Al-Nasaa’i
The Reality of Jinn
Ibn Hazm said:
"The jinn are real, and they are creatures created by Allaah. Among them are kaafirs and believers. They can see us but we cannot see them. They eat, have children and die. Allaah says (interpretation of the meanings):
"O you assembly of jinn and Mankind!"
"And the jinn, We created aforetime from the smokeless flame of fire"
"And of us some are Muslims (who have submitted to Allaah, after listening to this Qur'aan), and of us some are Al‑Qaasitoon (disbelievers those who have deviated from the Right Path)'. And whosoever has embraced Islam (i.e. has become a Muslim by submitting to Allaah), then such have sought the Right Path."
"And as for the Qaasitoon (disbelievers who deviated from the Right Path),
they shall be firewood for Hell"
"Verily, he and Qabeeluhu (his soldiers from the jinn or his tribe) see you from where you cannot see them"
"Will you then take him (Iblees) and his offspring as protectors and helpers rather than Me"
"Whatsoever is on it (the earth) will perish"
"Everyone shall taste death"
[Aal 'Imraan 3:185]."
Shaykh Ibn 'Uthaymeen (may Allaah have mercy on him) said:
"Undoubtedly the jinn can have a harmful effect on humans, and they could even kill them. They may harm a person by throwing stones at him, or by trying to terrify him, and other things that are proven in the Sunnah or indicated by real events. It was reported that the Messenger (peace and blessings of Allaah be upon him) gave permission to one of his Companions to go to his wife during one of the military campaigns -- I think it was the campaign of al-Khandaq -- as he was a young man who had recently got married. When he reached his house, he found his wife standing at the door, and he objected to that. She said to him, 'Go inside,' so he went inside and found a snake curled up on the bed. He had a spear with him, so he stabbed it with the spear until it died, and at the same instant as the snake died the man also died. It was not known which of them died first, the snake or the man. When the Prophet (peace and blessings of Allaah be upon him) heard of that, he forbade killing the harmless kinds of snakes that are found in houses, apart from those which are maimed or are streaked and malignant.
This indicates that the jinn may attack humans, and that they may harm them, as is known from real-life events. There are numerous reports which indicate that a man may come to a deserted area, and a stone may be thrown at him, but he does not see anybody, or he may hear voices or a rustling sound like the rustling of trees, and other things that may make him feel distressed and scared. A jinn may also enter the body of a human, either because of love or with the intention of harming him, or for some other reason. This is indicated in the aayah (interpretation of the meaning):
"Those who eat Ribaa will not stand (on the Day of Resurrection) except like the standing of a person beaten by Shaytaan (Satan) leading him to insanity"
In such cases, the jinn may speak from inside of that person and address the one who is reading verses from the Qur'aan over him; the reciter may take a promise from the jinn never to come back, and other things concerning which there are very many reports which are widespread among the people.
So the protection which will prevent the evil of the jinn is for a person to recite that which is narrated in the Sunnah as being effective in providing protection, such as Aayat al-Kurisy, for if a person recites Aayat al-Kursiy at night, he will continue to have protection from Allaah, and no shaytaan will come near him until morning. And Allaah is the Protector.'"
(Majmoo' Fataawa al-Shaykh Ibn 'Uthaymeen, 1/287-288)