The Gemora states that from the verse, “v’rapo yerapei” teaches us that a doctor is given permission to heal a sick person.
Rashi explains that if not for that verse, I might have thought that the doctor would be forbidden from healing him, for Heaven has decreed that he should be ill; it would be contrary to his destiny. The Torah teaches us that he may be cured.
The Rishonim ask from the Gemora above (81b) which cites a braisa: How do we know that one must return another lost person? The verse says, “And you will return it to him.” Is it not obvious then that a doctor is Biblically obligated to save a person from dying?
The Moishav Zekeinim answers that the Torah is teaching us that the doctor is allowed to charge for his services, for otherwise, I would have thought that since it is a mitzvah, he must do it for free.
Tosfos HaRosh answers that without the extra verse, I would have thought that a doctor may only heal a person when the sickness was man-induced. However, an illness that emanated from Heaven, it would be forbidden for the doctor to heal him, for it might be as if he is nullifying the word of God. The Torah teaches us that all sicknesses may be cured.
Tosfos Rabbi Yehudahh Hachasid explains why the Torah wrote v’rapo yerapei” twice: The Torah is teaching us that a second doctor may heal an ill person even after a first doctor was unsuccessful, for we might have thought that by the fact that the first doctor was unable to cure him, this is a proof that Hashem does not want him healed and it is forbidden for the second doctor to attempt to heal him. The Torah teaches us that even the second doctor is permitted to cure him.
The Hadar Zkeinim answers that if not for the extra verse, we would think that only a person who is drowning, where he is dying at that moment, is it permitted to save him. However, if one is sick and is dying slowly, perhaps it is forbidden to heal him. The Torah teaches us that even this is allowed.
The Ramban adds that this verse is necessary to teach the doctor that he should not say, “Why should I get involved? Perhaps I will err and cause the person to die.” The Torah is telling him that he need not be concerned for this.