The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam As-Sadi [may Allaah have mercy upon him] stated about health and disease:
The Islamic Sharee’ah brought the most complete guidance regarding them- commanded with everything that preserves and improves health and with what prevents diseases or reduces them as much as possible. It has given useful explanations on this subject matter revolving around the preservation and improvement of health, protection against all harmful things and activities, guarding against diseases before they occur (see footnote a) and treating them after they occur. (see footnote b)
Alongside this, it commanded that one relies and place complete dependence on Allaah (see footnote c), and to know that Allaah [The Exalted] is the Giver of blessings and the One Who repels harms by His Kindness, Power and Mercy (see footnote d), and by way of the many things He has facilitated as a means (to good health and protection against harm), which He taught His servants and commanded them to pursue.
Allaah also commanded that diseases should be dealt with through other than physical medicine, such as patience for the sake of Allaah, believing in Allaah and hoping for Allaah’s reward whilst facing adversity, because indeed this reduces the difficulty of diseases due to what the patient one – the one hoping for Allaah’s reward – receives of firm faith and certainty, as well as reward in this life and the next. (footnote e)
Commentary: Whoever examines the Sunnah – regarding drinks, nourishment and food – will find tremendous guidance in this affair that revolves around preservation of health, such as the statement of the Prophet [peace and blessings of Allaah be upon him], “The human being fills no worse vessel than his stomach. It is sufficient for a human being to eat a few mouthfuls to keep his spine straight. But if he must (fill it), then one third of food, one third for drink and one third for air.” [Sunan Ibn Maajah. Hadeeth Number 3349]
This hadeeth is a tremendous basis – for the preservation of health – that has been affirmed by many doctors, and enough is the fact that it is a statement of the Prophet, even if no doctor affirms it. Allaah said: [وَڪُلُواْ وَٱشۡرَبُواْ وَلَا تُسۡرِفُوٓاْۚ – Eat and drink but waste not by extravagance]. [Surah Al-A’raaf 31] (see footnote f)
Whoever wants to know what has been conveyed the Qur’aan and authentic Sunnah regarding health, let him (or her) read “At-Tibb An-Nabawiy – Medicine of the Prophet” from the book “Zaadul Ma’aadh” by Imaam Ibnul Qayyim. And with regards to preventing disease before it occurs, the Prophet said, “He who eats seven ‘Ajwa dates every morning, will not be affected by poison or magic on the day he eats them.” [Saheeh Al-Bukhaari. Hadeeth Number 5445]
Also reliance upon Allaah – to know that health and cure are only in the hands: Allaah said that Prophet Ibraaheem said: [وَإِذَا مَرِضۡتُ فَهُوَ يَشۡفِينِ – And when I am ill, it is He (Allaah) Who cures me]. [Surah Ash-Shu’araa. Aayah 80] (see footnote g)
Also in a supplication for a sick person, the Prophet stated:
[اللَّهُمَّ رَبَّ النَّاسِ أَذْهِبِ البَاسَ، اشْفِهِ وَأَنْتَ الشَّافِي، لاَ شِفَاءَ إِلَّا شِفَاؤُكَ، شِفَاءً لاَ يُغَادِرُ سَقَمًا – Allaahumma Rabbin Naas, Adh’hibil Ba’s, Ishfihi Antash Shaafi, Laa Shifaa’a illaa Shifaa’uka, Shifaa’an Laa Yughaadiru Saqamaa: Oh Allah, the Lord of the people! Remove the trouble and heal him (i.e. the sick person) for You are the Healer. No healing is of any avail but Yours; healing that will leave behind no ailment]. [Sahīh al-Bukhari. Hadeeth Number 5743]
The cure for an disease (illness) is in the hands of Allaah alone and one of Allaah’s Names is Ash-Shaafi (The Healer).
Patience: In the Sunnah, it is said to the sick person “,Tahooran InshaaAllaah- meaning, may this illness be a means to expiation of sins. Ibn Rajab mentioned a number of benefits for the sick person and the one afflicted with a calamity, and one of those benefits is that it strengthens a person’s attachment to Allaah. It maybe that a person was in a state of heedlessness, but when afflicted with an illness, he begins to take himself to account. Many people repented sincerely whilst on their sick bed, so this physical ailment brought him benefit in his religious affairs. (1)
Footnote a: What are the principles of medicine with the scholars of Islam: By Shaikh Abu Khadejah: https://abukhadeejah.com/what-are-the-principles-of-medicine-with-the-scholars-of-islam/
Footnote b: Striking a Balance in Health: Between Traditional and Conventional Medicine for Chronic Illnesses By Shaikh Abu Khadeejah: https://abukhadeejah.com/why-i-post-health-articles-on-my-site-and-top-12-tips-for-cancer-prevention/
It is not allowed to forcibly medicate a person… The Prophet stated, “Did I not forbid you from putting medicine in my mouth?” An-Nawawī said: “It is desirable that the sick person is not forced to take medication…By Shaikh Abu Khadeejah: https://abukhadeejah.com/taking-medicine-is-recommended-in-islam-for-the-one-who-is-sickbut-it-is-not-obligatory/
Footnote c: The Levels of Reliance Upon Allaah- By Shaikh Abu Hakeem:
Al-Lateef: The Subtle and Kind. The One Who is completely aware of the hidden details of all affairs and of that which will benefit the servants, and Who is kind to them, and causes that which is good for them to reach them by a means which they had no expectation of.
Al-Qadeer: The All-Powerful. The One Who is able to do all things; nothing renders Him incapable or wearies Him. The One Perfect in His Power. The One Who – by His power – created everything in existence. And with His power, He controls them, completes them and gives life and death to them. And with His power, He will resurrect His servants, and reward and punish them. Whenever He wills something, He says “Be” and it is.
Al-Qaadir: The Completely Able One. The One completely able to do anything He wills. Nothing renders Him incapable or wearies Him.
Ar-Rahmaan: The Extremely Merciful. The Merciful One Who has Mercy as His attribute. The One possessing tremendous and extensive Mercy. [Source: Names and Attributes of Allaah By Shaikh Abu Talhah (may Allaah have mercy upon him and his wife)].
Footnote e: Patience: https://atomic-temporary-194201713.wpcomstaging.com/2020/03/29/only-those-who-are-patient-shall-receive-their-rewards-in-full-without-hisaab-without-limit-calculation-and-estimation/
Footnote f: . Allaah said:[ يَـٰبَنِىٓ ءَادَمَ خُذُواْ زِينَتَكُمۡ عِندَ كُلِّ مَسۡجِدٍ۬ وَڪُلُواْ وَٱشۡرَبُواْ وَلَا تُسۡرِفُوٓاْۚ إِنَّهُ ۥ لَا يُحِبُّ ٱلۡمُسۡرِفِينَ – O Children of Adam! Take your adornment (by wearing your clean clothes), while praying and going round (the Tawaf of ) the Ka’bah, and eat and drink but waste not by extravagance, certainly He (Allah) likes not Al-Musrifun (those who waste by extravagance)].[Surah Al-A’raaf 31]
Imaam As-Sadi said, meaning eat and drink from that which Allaah has provided you of the good and lawful things, but do waste not by extravagance in doing so. Extravagance can either take place when one consumes more than what is sufficient by eating too much of foods and having a lot of drinks that are harmful to the body, or exceeding the limits in choosing the most luxurious and fanciest of foods, drinks and clothing, or exceeding the limits in what is permissible until it leads to what is impermissible. Certainly Allaah does not like those who are wasteful by extravagance, because exceeding the limits angers Allaah and it is harmful to person’s body and livelihood, until this may even lead a person to be unable to spend on what is necessary. [An Except from Tafseer As-Sadi. Slightly paraphrased]
Footnote g: [وَإِذَا مَرِضۡتُ فَهُوَ يَشۡفِينِ – And when I am ill, it is He [Allaah] Who cures me]. [Surah Ash-Shu’araa. Aayah 80] – Meaning: When I become sick, none is able to heal me, except Allaah, by way of the means that may lead to recovery [i.e. by His Will]. [Tafseer Ibn Katheer]
Abdullah Ibn Mas’ood [may Allaah be pleased with him] said, “Allaah’s Messenger [peace and blessings of Allaah be upon him] said, ‘Allaah did not send down any disease except that he also sent its cure.” In another narration, the Messenger said, ‘One who has knowledge of it knows it, and one ignorant of it is ignorant’”. [Sunan Ibn Mājah 3438 and declared authentic by Imaam Albaanee in Sisilah As-Saheehah 4/208]
The Messenger said, “Treat your sick by giving Sadaqah”. [Hadeeth declared Hasan by Imaam Albaani [rahimahullaah] in Saheeh Al-Jaami As-Sagheer Wa Ziyaadah 3358]
AbuBakr Al-Khubaaziy [may Allaah have mercy upon him] said, “I had a very dangerous illness, so a neighbour of mine saw me and said, ‘Act upon the statement of Allaah’s Messenger [peace and blessings of Allaah be upon him], ‘Treat your sick by giving Sadaqah’. It was summertime, so I bought many watermelons and gathered a group of poor people and children. They ate and then supplicated for me to be cured. By Allaah! I did not reach the next morning except that Allaah granted me wellbeing’”. [Siyar A’laam An-Nubulaa 18/44]
[Ref 1: From 44mins 24secs to 54mins 08secs. https://www.al-badr.net/detail/6y71LsHDZr paraphrased]