Midrasz do Szabbat 7:5

Every man who is ill and bathes in those waters, will be healed, as it is said, "In every place whither the rivers come, he shall live… and every thing shall live whithersoever the river cometh" (Ezek. 47:9). Every man who has a wound will be healed by taking of their leaves and applying them to his wound, as it is said, "And the fruit thereof shall be for meat, and the leaf thereof for healing" (Ezek. 47:12). What is the meaning of "for healing"? Rabbi Jochanan said: For a laxative; || suck its leaves and one's food is digested.