Question: "What is the significance of the healing trees with leaves for medicine (Ezekiel 47:12)?"
Answer: The prophet Ezekiel is shown healing trees with leaves for medicine (Ezekiel 47:12) as part of a series of visions that God gave him regarding the future of Israel (Ezekiel 40:2). In those visions (Ezekiel 40—48) God shows Ezekiel a future temple in Jerusalem (Ezekiel 40—43), sets new rules for a coming prince and the future priests (Ezekiel 44—45), describes the sacrifices to take place during that time (Ezekiel 46), details the topography and boundaries of the restored land of Israel, and numbers the gates of Jerusalem (Ezekiel 47—48).
As God was showing Ezekiel the massive temple that will exist in the future, Ezekiel saw that there was water flowing from under the south side of the temple to the east side of the temple (Ezekiel 47:2). For roughly a thousand cubits to the east (1,700 feet) the water was ankle deep (Ezekiel 47:3). For another thousand it was knee deep, and at the third thousand the water was roughly waist deep (Ezekiel 47:4). Beyond that it was too deep to walk through (Ezekiel 47:5). The river flowed into the sea and made the seawater fresh and teeming with life (Ezekiel 47:8–10). As Ezekiel observed the banks of the river, he saw many trees on both sides (Ezekiel 47:6–7). These trees provided food, and their leaves never withered. “They will bear fruit every month, because their water flows from the sanctuary. Their fruit will be for food, and their leaves for medicine” (Ezekiel 47:12, NKJV).
Ezekiel’s description of a river lined with healing trees matches some aspects of a vision in Revelation 22, where John is shown a similar scene. In the New Jerusalem, John sees the river of life, which comes from God’s throne and the Lamb’s throne (Revelation 22:1). On both sides of this river was the tree of life, which will bear fruit every month, and which had leaves “for the healing of the nations” (Revelation 22:2).
In both Ezekiel and Revelation, the tree of life provides fruit for food each month—a continual harvest, with no dormancy—and the tree heals, having leaves for medicine. Ezekiel and John are describing similar time frames and providing a glimpse of what Jerusalem will look like in the coming kingdom of Jesus. The first thousand years of that kingdom (Revelation 20:2–5) take place prior to God’s final judgments (Revelation 20:11–15), and this is what Ezekiel describes. After that, there will be a new heaven and earth and a new Jerusalem, which will be the epicenter of God’s kingdom from then on (Revelation 21:1–3ff); this is what John describes. In the millennium and the New Jerusalem, the tree of life will be the (primary, at least) healing tree with leaves for medicine (Revelation 22:2).
With the description of the tree of life, the Bible comes full circle. Human history started out with the tree of life in the center of the Garden of Eden. But when Adam sinned, he and all his descendants were barred from accessing that tree, and they were doomed. Then Christ came to save sinners, and those who trust in Him will be granted full access to the tree of life once again. It seems that, in the future kingdom of God, the tree is growing everywhere, not just in one place. Because of the amazing grace of God, we will have life in abundance, partaking of the tree’s unending fruit and benefiting from the healing properties of its leaves like medicine.