Amazingly, although the Prophet (PBUH) lived in one of the poorest and most ignorant nations 14 centuries ago, he was guided by Allah to teach Muslims and the whole world ever since that “There is no disease that Allah has created, except that He also has created its treatment.” [Bukhari]

At that time, when treatment with magic and the like was widespread all over the world, such a statement by the Prophet was a wide leap forward in human knowledge; a leap that could only emanate from the ever-Knowing Allah SWT. The Prophet’s guidance further inspired Muslims to search and discover effective medicines, when he said, in a more complete narration of the hadith: "Allah has never created a disease but created its treatment, that is known by some people and unknown to others, except death." [At-Tabarani]

The reason that Muslims advanced so much in medicine is because the Prophet (PBUH) had told them that for every disease there is a cure, and that they should seek treatment. He pointed to many cures himself. He encouraged the women of his household to learn medicine from those who knew it. Women, in the time of the Prophet (PBUH), excelled in medicine. The Prophet had pitched a tent in the yard of his mosque in Medina and appointed a lady named Rufaidah (RA) to run it as a field hospital, to nurse the wounded and care for homeless newcomers to Medina. [Tarikh at-Tabari] 

Muslims are requested to seek medication from experts, as in the following hadith: “Allah has sent down both the disease and the cure, and He has appointed a cure for every disease, so treat yourselves medically, but use nothing unlawful.” [Abu Dawud] Again, this was an outstanding progressive piece of advice 14 centuries ago that could only come from the divine guidance of Allah SWT.
 
Once Prophet Muhammad (PBUH) visited a sick person. He said, “Call a physician for him.” One of the attendants said, “Even you say this, Prophet of Allah?” Prophet Muhammad replied, “Yes.” [Bukhari]

Also, as a precaution to lessen the probability of infection, the Prophet (PBUH) warned Muslims against associating with the sick: “A sick person should not be taken to one who is healthy.” [Bukhari]

Islam teaches us many things in the field of healing people. In addition, the Prophet (PBUH) urged us to recite some supplications in case one falls victim to illness. He used to say every morning and night, “I seek refuge in the Perfect Words of Allah (the Quran) from the evil of what He has created.” [Muslim]

These Ahadith indicate there are causes for whatever occurs in this world and also removal of these causes. The Prophet's statement that there is a cure for every disease might include both the curable and the humanly incurable diseases, for Allah SWT may have hidden these types of cures from mankind and blocked their path to acquiring them. 

The Prophet (PBUH) said that the disease ends when the proper cure is applied to it, indicating that there is an opposite for every creation and thus there is an antidote for every disease. He has also stated that when the proper remedy and the disease meet, recovery from the illness occurs. When the sick person and the disease are not treated with the suitable medicine, cure and recovery does not occur. Also, when the time is not suitable for the cure, or when the body is unable or unsuitable for the prescribed medicine, the cure will not be effective. When all circumstances are favourable, then the cure will surely be effective.

Conclusion
Muslims are commanded to seek and take the appropriate medicine, while indicating that this action does not contradict dependence on Allah SWT alone for everything. Just like when a person satisfies his hunger and thirst, or reacts to being hot or cold, does not contradict the dependence on Allah SWT. A person should bear in mind first that it is Allah SWT who has the power of healing all people; no one has this power except Him.

Iman (faith) and Tawakkul (trust) have to be the uttermost important part of a Muslim’s belief. Since this material world has been classed as Darul Asbaab (a world of means), it is necessary to take medication for one’s illness. To have trust in Allah is to search for a cure, which would be classed as the highest grade of Tawakkul.
 

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Source: Healing with the Medicine of the Prophet
by Imam Ibn Qayyim Al-Jauziyah