Our religion came as a guidance for each one of us, what is narrated from the Sunnah complements what there is in the Qur’an and these are the main principal sources for us Muslims to follow and to use as guidance.
Allah says in Surah Yunus verse 57, “Oh mankind! There has come to you a good advice from your Lord (i.e. the Qur’an, ordering all that is good and forbidding all that is evil), and a healing for that (disease of ignorance, doubt, hypocrisy and differences, etc) in your breasts, – a guidance and a mercy (explaining lawful and unlawful things, etc) for the believers” Allah says in Surah Al-Isra verse 82,
وَنُنَزِّلُ مِنَ ٱلْقُرْءَانِ مَا هُوَ شِفَآءٌ وَرَحْمَةٌ لِّلْمُؤْمِنِينَ ۙ وَلَا يَزِيدُ ٱلظَّـٰلِمِينَ إِلَّا خَسَارًا
“And we sent down from the Qur’an that which is healing and a mercy to those who believe (in Islamic Monotheism and act on it), and it increases the Zalimun (polytheists and wrong-doers) nothing but loss” Imam Ibn al-Qayyim said in his excellent work, Zaad al-Ma’aad (3/97-98), after discussing the benefits of honey in relation to the man who was advised by the Messenger peace and blessings be upon him to treat the ailment of his stomach with honey:
His medicine peace and blessings be upon him is not like the medicine of the physicians, for the medicine of the Prophet peace and blessings be upon him is certain, definitive, emanating from (divine) revelation, the lantern of prophethood, and perfection of reason. As for the medicine of others, most of it is conjecture, presumptions and experimentation.
As for the absence of benefit to many of the ill from the Prophetic medicine, that is not to be shown rejection because only those benefit with it who wholeheartedly accept it, believe firmly in its ability to cure, and perfectly accept it through faith and submission.
This Qur’an which is the cure for what is in the hearts, if it is not accepted with such acceptance, the healing of the hearts will not be attained by its treatments. Rather, it only increases the hypocrites in evil on top of their evil, and disease on top of their disease. And so where does the bodily medicine stand with respect to it. The Prophetic medicine is not suited except for wholesome bodies, just as the cure of the Qur’an is not suited except for good souls and lively hearts.
The people turning away from the Prophetic medicine [in bodily matters] therefore is like them turning away from seeking cure from the Qur’an which is indeed the beneficial cure. And this is not because of any deficiency in the treatment, but due to the vileness of the bodily disposition and corruption of the diseased location and nonacceptance of (the healing capacity)… and Allaah is the one who grants success.