It should be noted that ruqyah is one of the types of remedy prescribed in Islam, but there are certain conditions for it to be beneficial and acceptable, just as physical medicine has conditions for it to be suitable.
Al-Haafiz Ibn Hajar (may Allah have mercy on him) said:
The scholars are unanimously agreed that it is permissible to use ruqyah if three conditions are met: it should based on the words of Allah, may He be glorified and exalted, or His names or His attributes; it should be in Arabic or in words the meaning of which can be understood; and it should be accepted that ruqyah does not have any effect in and of itself, rather that happens by the will and decree of Allah.
End quote from Fath al-Baari.
The scholars have stipulated that the ruqyah should be in Arabic or in words that are known and understood, lest the words of the one who does it constitute shirk or could lead to shirk, without the one for whom it is done realising that. This problem is more serious if the one who is performing ruqyah is one of the People of the Book, who are people of shirk. It is to be expected that they will perform ruqyah by saying things that are in accordance with their religion, especially if they do so in a language that the one for whom it is done does not know, and especially if the one who is seeking the ruqyah has gone to them in their churches or monasteries.
This is the reason why some of the scholars did not allow People of the Book to perform ruqyah for Muslims.
Ibn ‘Abd al-Barr (may Allah have mercy on him) said:
Maalik did nor approve of ruqyah done by the People of the Book. That was because – and Allah knows best – it cannot be known whether they will recite from the Book of Allah, may He be exalted, or use words that constitute witchcraft.
End quote from al-Istidhkaar, 9/376
For that reason, those scholars who allowed the ruqyah of the People of the Book stipulated that the ruqyah should be done using words that are known to be the words of Allah or dhikr.
See al-Umm by al-Shaafa‘i, 7/228
There is no doubt that to be on the safe side with regard to one’s religious commitment and to avoid falling into error, one should keep away completely from asking the People of the Book for ruqyah, especially since their insincerity towards the Muslims is well known. Indeed it is also well known that they either seek the help of the jinn and shayaateen in what they do, which means that their ruqyah comes under the heading of witchcraft, or they bring the cross close to the one who is sick and seek the help of their brethren of the shayaateen by doing so, according to what is mentioned above of the words of Ibn al-Teen (may Allah have mercy on him).
The issue of ruqyah is easy, in sha Allah and there are many righteous Muslims who are able to do it well. There is nothing more beneficial than a person performing ruqyah for himself, reciting the words of Allah or du‘aa’s that are soundly narrated from the Prophet (blessings and peace of Allah be upon him).
Hence the scholars of the Standing Committee issued a fatwa stating that that (going to a Christian priest) is not permissible, when they were asked:
The remedy for seizures among us in Egypt is to go to the church, especially the church of Mary Jarjis, or to go to practitioners of witchcraft and charlatans who are widespread in the villages. Sometimes that brings results. Is it permissible to do that? Please note that if the person who has a seizure is not treated quickly, he will die.
What is the remedy prescribed by Allah for this sickness, as there is a remedy for every disease except old age?
The scholars of the committee replied:
It is not permissible to go to the church to treat seizures, or to go to the practitioners of witchcraft or the charlatans. As for permissible remedies, he may be treated by means of ruqyahs that are acceptable in Islam, such as reciting Qur’aan, e.g., al-Faatihah, Qul Huwa Allahu Ahad (Soorat al-Ikhlaas), al-Mu‘wadhatayn (the last two soorahs of the Qur’aan in which refuge with Allah is sought) and Aayat al-Kursiy, as well as dhikrs and du‘aa’s that are soundly narrated from the Messenger (blessings and peace of Allah be upon him). And Allah is the source of strength. End quote.
Fataawa al-Lajnah, 1/292-293
And Allah knows best.