Healing of the Sick in the Geulah

In the time of Geulah, everyone will be completely healthy. All the sick will be healed, and there will no longer be blind, deaf, lame, or mute people.

Source of the Destiny

"Then the eyes of the blind shall be opened, and the ears of the deaf shall be unstopped. Then shall the lame man leap as a hart, and the tongue of the dumb sing." — Yeshayahu 35:5-6

In Stages

Initially Hashem Heals the Blind

"When He (Hashem) comes to heal the world, He first heals the blind," in a way that they become "sagi-nahor" in a positive sense—they have an abundance of light in a literal sense (in a way that doesn't diminish their physical sight). Consequently, they have the ability to read and study Torah from regular written letters—like ordinary people.

Those who arise during Techiyas Hameisim (Resurrection of the Dead) will arise as they were when they passed away, and afterward they will be healed.

Even doctors will have livelihood from everyone being healthy.

Exception

Rabbi Levi said: In the future, all will be healed except for the snake and the Gibeonites. The snake, as it is said: "And dust shall be the serpent's food. They shall not hurt nor destroy, etc." The Gibeonites: "And they that serve the city shall serve it out of all the tribes of Israel." — Bereishis Rabbah 20:3

The snake will be a great servant, as it was before the sin of the Tree of Knowledge, but one of the (ten) curses that the snake received—that (everything) it eats (will taste like) dust—will remain even in the future time (as it is written, "and dust you shall eat all the days of your life"—including the days of Moshiach).

It Has Already Happened

Expanded topic – It Has Already Happened

• At the time of Matan Torah (Giving of the Torah), all the sick were healed, but unlike then, in the time of Geulah, the healing of the sick will be permanent.
• The healing of Moshe Rabbeinu from his tzaraas.
• The healing of Naaman, army commander of the king of Aram, by Elisha the prophet.