Exodus 15:27

The people murmured against Moses, saying, “What shall we drink?”

Then he cried to the LORD. The LORD showed him a tree, and he threw it into the waters, and the waters were made sweet. There he made a statute and an ordinance for them, and there he tested them.

He said, “If you will diligently listen to the LORD your God’s voice, and will do that which is right in his eyes, and will pay attention to his commandments, and keep all his statutes, I will put none of the diseases on you which I have put on the Egyptians; for I am the LORD who heals you.”