In The Name of Allah, The Most Merciful, The Bestower of Mercy.

Good Health and Disease

Imam As-Sadi [may Allah have mercy upon him] stated:

The Islamic Shariah brought complete guidance in this regard, commanding everything that preserves and enhances health, as well as what prevents or reduces (the risk) of diseases. It provided useful explanations on this subject that centred around the preservation and improvement of health, protection against all dangerous things and activities, guarding against diseases before they emerge, and curing them when they do. (See footnote a) Along with this, Islam commanded one to rely on Allah and to know that Allah [The Exalted] is the Bestower of blessings and the One Who repels harm through His Kindness, Power, and Mercy, and through the many things He has facilitated as a means (of wellbeing), which He taught and ordered His servants to pursue.

Allah also commanded that diseases be treated in ways other than physical medicine, such as having patience for the sake of Allah, believing in Allah, and hoping for Allah’s reward while facing adversity because this indeed reduces the difficulty of diseases, and the patient one – the one hoping for Allah’s reward – receives firm faith and certainty, as well as reward in this life and the next. Similarly, when calamities and hardships occur, Islam commands that a person should not be subdued, his heart and resolve weakened, and become overpowered by those imaginations that are deadly diseases. Many small and mild diseases cause considerable agony due to the heart’s weak and fragile state, as well as being misled by illusions and imaginations; (but) when the heart relies on Allah, its faith and reliance are reinforced, and fear disappears. This is an observed and clearly perceived phenomenon. (see footnote b) The Islamic religion enjoins two things at the same time: using the beneficial means, complete dependence on Allah, acquiring benefits, and repelling harm according to one’s ability. (1)
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Footnote a: visit links by Shaikh Abu Iyaadh and Shaikh Abu Khadeejah:
https://twitter.com/AbuIyaadSP/status/692338610272649216?lang=en-GB
https://abukhadeejah.com/health-sickness-in-the-light-of-islaam/

Footnote b: Very beneficial series of lectures by Shaikh Abu Hakeem:

https://www.salafisounds.com/category/books-taught/the-levels-of-reliance-upon-allah-by-abu-hakeem/

Allah’s Messenger [peace and blessings of Allah be upon him] said, “Treat your sick by giving Sadaqah”. [Saheeh Al-Jaami As-Sagheer Wa Ziyaadah 3358]

AbuBakr Al-Khubaaziy [may Allah have mercy upon him] said, “I was suffering from a potentially fatal ailment, so a neighbour saw me and said, ‘Act on what Allah’s Messenger said, ‘Treat your sick by giving Sadaqah’. Since it was summer, I purchased many watermelons and gathered a group of children and poor people, then they ate and supplicated for my recovery. By Allah! I did not reach the following day except that Allah granted me wellbeing”. [Siyar A’laam An-Nubulaa 18/44]

[An Excerpt from Ad-Deenus Saheeh Yahillu Jamee al-Mashaakil (The right religion is the answer to every problem)-Page 10. slightly paraphrased]