If G-d wants us to serve Him properly, why does he bring sickness upon people, which just hinders their ability to do His will?
According to Jewish belief, not only did Adam and Eve have all their needs taken care of in Edenbefore the sin, there was no sickness at all either. Their pure spiritual state precluded sickness of any type.
Even after the sin, their needs were greatly taken care of, and even the climate of the world was relatively moderate. This was in order to facilitate a physically easy lifestyle with the purpose of freeing humanity for the service of G-d.
One of the classical commentaries actually explains that this is the reason for the great longevity of the early generations of mankind: Because people were still on a relatively high spiritual level despite being banished from Eden, they were not plagued by sickness, disease and infirmity.
Therefore, only after mankind stopped serving G-d did people really start to suffer sickness. By departing from G-d, we forfeited the purpose of good health. Rather than G-d bringing sickness upon us, then, we brought it upon ourselves.
However, by the same token, sickness becomes a tool through which one comes close to G-d. It is to be viewed as a reminder that we have somehow strayed off the right path, should repent and pray to G-d to heal us and protect us. Seeking remedies without this ingredient in the prescription is considered brazen and ungrateful.
The Talmud (Berachot 9b) discusses how the righteous King Hezekiah eliminated the famous “Book of Remedies of Solomon”. On the surface this seems like a bad move – the remedies in that book were able to heal any possible sickness man might have. In removing the book, he was effectively perpetuating the maladies of mankind. Yet the Talmud says the wise men of Hezekiah agreed. Why? Because people came to rely on the remedies alone and no longer used the maladies as an opportunity to repent, pray to and come close to G-d.
Once a certain Jew with a serious illness came before Rebbe Mordechai of Nishchiz complaining that he had been to all the best doctors but none could find a cure. The Rebbe asked if had gone to seek the help of the Professor in Anipoli. The Jew was surprised to hear of a specialist that he had not yet been referred to, but the Rebbe assured him that the inhabitants enjoy unusually good health there thanks to the Professor. The Jew set out for Anipoli, but when he arrived, not only was he told there was no Professor, but there was not even a simple doctor in such a small town. Perturbed, the Jew asked his coreligionists, “So what do you do when you’re sick?” “We pray to G-d for a cure”, they replied.
Disappointed with the Rebbe’s mistaken information, he returned to the Rebbe with a report of what happened. The Rebbe asked, “So what do they do when they get sick?” When the Jew relayed their answer, the Rebbe replied, “They must be doing something right – and now you know the meaning of the verse, “I am G-d your Healer” (Ex. 15:26).