Praise be to Allah.
Generally speaking, medical treatment or seeking a cure is allowed, because of the report of Abu’l-Darda’ (may Allaah be pleased with him) who said: “The Messenger of Allaah (peace and blessings of Allaah be upon him) said: ‘Allaah has sent down the disease and the cure, and has made for every disease the cure. So treat sickness, but do not use anything haraam’” (Reported by Abu Dawood, 3376), and the hadeeth of Usaamah ibn Shurayk (may Allaah be pleased with him) who said: ‘The Bedouin said, “O Messenger of Allaah, should we not treat sickness?” He said: “Treat sickness, for Allaah has not created any disease except He has also created the cure, except for one disease.” They said, “O Messenger of Allaah, what is it?” He said: “Old age.”’” (Reported by al-Tirmidhi, 4/383, no. 1961. He said: This is a saheeh hasan hadeeth. See also Saheeh al-Jaami’, 2930).
The majority of scholars (Hanafi and Maaliki) said that medical treatment is mubaah (permitted). The Shaafi’is, and al-Qaadi, Ibn ‘Aqeel and Ibn al-Jawzi among the Hanbalis, said that it is mustahabb (recommended), because of the hadeeth “Allaah has sent down the disease and the cure, and has made for every disease the cure. So treat sickness, but do not use anything haraam,” and other ahaadeeth which contain instructions to seek cures. They said: the fact that the Prophet (peace and blessings of Allaah be upon him) used cupping and other kinds of treatment indicates that medical treatment is permitted. For the Shaafi’is, treatment is mustahabb when there is no certainty that it will be beneficial, but when treatment is certain to be beneficial (such as putting a dressing on a wound), then it is waajib or obligatory (an example would be blood transfusions in certain cases).
(See Haashiyat Ibn ‘Aabideen, 5/215, 249; al-Hidaayah Takmilat Fath al-Qadeer, 8/134; al-Fawaakih al-Dawaani, 2/440; Rawdah al-Taalibeen, 2/96; Kashshaaf al-Qinaa’, 2/76; al-Insaaf, 2/463; al-Aadaab al-Shar’iyyah, 2/359ff, Haashiyat al-Jumal, 2/134).
Concerning the saheeh ahaadeeth that speak about medical treatment, Ibn al-Qayyim said: This does not contradict tawaakul (putting one’s trust in Allaah), just as warding off hunger, thirst, heat and cold does not contradict tawakkul. The essence of tawaakul is not complete without resorting to the means which Allaah has set out in order for us to achieve results both according to His decree (qadr) and His laws (shar’). Not using these means is contrary to tawaakul: it goes against and undermines the command and wisdom of Allaah, although the one who neglects the means may think that this makes his tawakkul stronger. Ignoring the means is a sign of helplessness that goes against the true essence of tawakkul, which is that the heart relies on Allaah to bring the slave whatever will benefit him in this world and the next, and to protect him from whatever may harm him in this world and the next. But along with this reliance, it is essential to take the appropriate means, otherwise he will be going against the wisdom and command of Allah. Helplessness should not be taken as a sign of tawaakul, nor should tawakkul make a person helpless.
(Zaad al-Ma’aad, 4/15. See al-Mawsoo’ah al-Fiqhiyyah, 11/116)
In summary, therefore, seeking a treatment or cure is not obligatory according to the scholars, unless – according to some – it will definitely be of benefit. Since in the situation described in the question there is no certainty that treatment will be of benefit, and indeed it is likely to cause suffering to the patient, then there is nothing at all wrong with not giving the treatment. The patient should not forget to put his trust in Allaah and seek refuge in Him, for the gates of Heaven are open to those who call on Allaah. He may also seek treatment (ruqya) by reciting Qur’aan, such as reading al-Faatihah, al-Falaq and al-Naas over himself. This will benefit him psychologically and physically, as well as bringing him reward. Allaah is the Healer and there is no healer but He.