A General Cure for all diseases by Ruqyah Al Elahiyyah (Allah's Spell)
It is mentioned in Abu Dawood (narrated by Abu Darda Radi Allaho Anh) who said, I heard Prophet Mohammad Salallaho Alaihe Wasallam saying, whoever gets sick or his brother is sick, then he should recite the words :
"Our LORD is the LORD in heavens & skies, Your Name is Holy, Your Order is Firm in the heavens & earth, and as Your Mercy overspreads the skies, please Descend Your Mercy on the earth, & please Forgive our sins & mistakes, You are the LORD of pious people, Send Mercy from Your treasures of Mercy & CURE from Your treasures of CURE on this disease & pain" and if a person recites this Dua, he will be Given the cure.
Also narrated by Saheeh Muslim, Abu Saeed Khudri Radi Allaho reported that angel Jibreel came to Prophet Muhammad Sallallaho Alaihe Wasallam & said "O Muhammad Sallallaho Alaihe Wasallam, are you suffering from a pain or a disease? Prophet Muhammad Sallallaho Alaihe replied "Yes", so Jibreel said :
In the name of Allah, I blow the spell on you, for protection from all evils, protection from the evil of all humans, protection from the evil eye of every jealous person, may Allah Give you the Shifa (Cure), and in the name of Allah, I blow the spell on you.
Someone may object on the Hadith of Abu Dawood, which narrates that Ruqyah (blowing the spell) is only valid for nullifying the affects of an evil eye or for the sting of a poisonous creature; "Humah" means all kinds of poisonous animals like a snake, a scorpion, etc.
The answer is that from the above Hadith, Prophet Muhammad Sallallaho Alaihe Wasallam never intended to invalidate the Ruqyah for purposes other than the evil eye or the sting of a poisonous animal, rather the Hadith indicates that Ruqyah brings the most powerful results against the evil eye & the poisonous sting.
When Sahl Bin Hanif Radi Allaho Anh suffered with the evil eye, he asked Prophet Muhammad Sallallaho Alaihe Wasallam if Ruqyah has the Khair (benefit), so Prophet Muhammad Sallallaho Alaihe Wasallam replied to him, "Ruqyah is for the evil eye & for the poisonous sting".
Narrated by Abu Dawood on behalf of Anas Radi Allaho Anh, that Prophet Muhammad Sallallaho Alaihe Wasallam said "Ruqyah (blowing the spell) is only for the evil eye or Humah (poisonous sting) or for the Fasaad (spoilage) of blood".
Also narrated by Saheeh Muslim on behalf of Anas Radi Allaho Anh, that Prophet Muhammad Sallallaho Alaihe Wasallam allowed Ruqyah for the evil eye, poisonous sting and the Namlah (which is the abscess or a carbuncle).