Exodus 15:25-26

25So he cried out to Adonai, and Adonai showed him a tree. When he threw it into the waters, they were made sweet. There He made a statute and an ordinance for them, and there He tested them.

26He said, “If you diligently listen to the voice of Adonai your God, do what is right in His eyes, pay attention to His mitzvot, and keep all His decrees, I will put none of the diseases on you which I have put on the Egyptians. For I am Adonai who heals you.”